BI-RADS® Lexicon for Calcifications and Individual Calcification Shapes

The American College of Radiology (ACR) Breast Imaging Reporting and Data System (BI-RADS®) lexicon has a good section on description and assessment of calcifications. In the mammography report, radiologists use BI-RADS® terms to describe calcification forms, distribution, location, associated findings, and whether any change has occurred since the previous study. BI-RADS® terms are powerful descriptors that help the clinician understand the seriousness of the finding, such as fine linear branching in cancers. The BI-RADS® terms also help the radiologist classify calcifications into BI-RADS® assessment categories, which prompt patient management (Boxes 3-1 and 3-2). For example, the BI-RADS® term pleomorphic, which is suspicious for cancer, would prompt the radiologist to classify the calcifications into a BI-RADS® category 4, which calls for biopsy to be performed, whereas the term large rodlike, which indicates benign secretory disease, would be classified as a BI-RADS® category 2 and would be dismissed.

BI-RADS® terms are based on calcification morphology. Knowing the underlying anatomic structure in which calcific particles form helps the radiologist to understand why some calcific shapes have specific morphologies and why they suggest benign or malignant disease. An example of how anatomic structures influence calcification shapes are the round calcifications that form in round benign terminal breast acini or lobules. These benign calcifications take on the round shape of the acini in which they form, and hence, are round, regular in shape, densely calcified, and sharply marginated (Fig. 3-3A to C). The BI-RADS® term for these calcifications is punctate; they are usually benign.

Figure 3-3 A, Schematic representation of calcifications in benign disease. Calcifications in benign disease form in the acini or lobuli of the duct, so they look round (left). On the mammogram, these calcifications will be sharply marginated, round, dense, and punctate because they form in round structures (right). These round, benign-appearing calcifications are the result of benign fibrocystic change. Mammogram (B) and core biopsy specimen (C) of two groups of round calcifications in proliferative fibrocystic change; biopsy was performed because of change in the appearance of the calcifications since the previous screening mammogram. D and E, Amorphous or indistinct indeterminate calcifications on core biopsy caused by proliferative fibrocystic disease. F, Amorphous calcifications in fibrocystic change. G, Punctate and amorphous calcifications in fibrocystic change. H to K, Punctate and amorphous calcifications in intermediate-grade ductal carcinoma in situ (DCIS). L, Schematic of DCIS in cross-section. Note the spaces in the DCIS tumors, in which the calcifications form.

The BI-RADS® term amorphous or indistinct describes indeterminate calcifications that are tiny, roundish, flake-shaped particles that are too small and vague to allow further characterization. Both benign and malignant processes produce this type of calcification (Box 3-3). Benign fibrocystic disease and sclerosing adenosis produce blunt duct extension and ductal dilatation that result in indeterminate amorphous or indistinct calcifications (see Fig. 3-3D to F). However, some amorphous or indistinct calcifications can also form in ductal carcinoma in situ (DCIS) (see Fig. 3-3G to J). This overlap between benign- and malignant-appearing calcifications results in “false-positive” biopsies and accounts for up to 75% of benign biopsy results from procedures prompted by calcifications.

Calcifications that develop in DCIS or invasive ductal cancer grow in breast ducts and have classic appearances (Fig. 3-4A and B). The ACR BI-RADS® term for these calcifications is fine linear or fine linear branching (casting) calcifications. These calcifications have linear forms because DCIS grows in branching ducts and the calcifications form within the DCIS, making tiny irregular casts of the duct. These calcifications may look like little broken needles with pointy ends or may have a “dot-dash” appearance with both round and linear shapes. Calcific casts of tumors growing in duct branches form X-, Y– or Z-shaped calcifications. Radiologists describe these classic calcifications as fine linear, fine linear branching, casting, or pleomorphic in the report to reflect their concern for cancer. This is in contradistinction to benign-appearing round, punctate calcifications (see Fig. 3-4C to E).

Figure 3-4 A, Schematic of individual casting calcification forms in ductal carcinoma in situ (DCIS). In DCIS, calcifications form in the middle of necrotic tumors growing in breast ducts (left). The ACR BI-RADS® term for suspicious bizarre linear or branching particle-shaped calcifications is fine linear or fine linear branching (casting) calcifications because the calcifications are in a line or form a cast of the duct. B, Photographic magnification of clustered pleomorphic calcifications in DCIS. Note the branching shape of the calcification in the uppermost part of the cluster. C and D, Suspicious pleomorphic calcifications in clusters, linear, and linear branching distributions have bizarre and linear individual forms within each cluster. These are typical of DCIS. E, Photographic magnification of part D.

Another suspicious calcification form described by the ACR BI-RADS® lexicon is pleomorphic or heterogeneous (granular). This term reflects very tiny, irregularly shaped calcific particles that look like bizarre broken glass shards forming inside pockets of necrotic tumors, such as the micropapillary or cribriform forms of DCIS (Fig. 3-5). The individual calcifications are roughly round in shape but have irregular borders, are faint, smaller than 0.5 mm, and vary in size and density. A cluster containing granular calcifications may not exhibit casting or linear forms but should still be considered suspicious even in their absence. Occasionally, granular calcifications form in a duct and look like sand stuffed in a plastic straw. Unfortunately, benign disease occasionally mimics DCIS and also forms granular calcifications (see Fig. 3-5B to G).

Figure 3-5 A, Schematic of linear/branching calcifications versus granular calcifications. In ductal carcinoma in situ (DCIS), linear or branching calcifications form if the necrotic center extends along the duct (left). Amorphous or granular calcifications in DCIS form in small pockets of DCIS and pack the duct with roundish, but irregular, calcific particles (right). Photographic magnification of the granular calcifications in DCIS shows variability in size and density and a “million” tiny calcifications almost too faint to discern in invasive ductal cancer (B) and DCIS (C). D, Clustered, faint granular and amorphous calcification in DCIS. Amorphous or indistinct calcifications also can be present in benign sclerosing adenosis or fibrocystic change. In nonproliferative fibrocystic change, granular calcifications on mammography (E) and stereotactic core biopsy (F) show the overlap between benign and malignant calcifications. G, Pleomorphic linear calcifications in DCIS. H, Amorphous calcifications in DCIS. I, Amorphous and pleomorphic calcifications in DCIS. J, Amorphous and fine linear calcifications in DCIS. K, Granular calcification cluster in DCIS.

DCIS is classified into high-, intermediate-, and low-grade forms. The description of the histologic architecture of DCIS uses words such as comedocarcinoma, which describes the appearance of the comedos of extruded thick tenacious material that resembles a pimple and often calcifies centrally. The terms micropapillary, solid, and cribriform reflect the DCIS architecture in the duct.

It used to be thought that specific suspicious calcification forms suggested specific DCIS histologies, but this is a myth. Although comedo-type DCIS calcifications are often “casting” and micropapillary and cribriform DCIS calcifications are often “granular,” Stomper and Connolly showed that DCIS subtype calcification forms overlap within histologic types. Casting or granular calcifications do not predict a specific DCIS histology, nor do they predict whether cancer is microinvasive or invasive. Casting or granular calcifications can form in DCIS and in microinvasive or invasive ductal cancer. Thus, the radiologist cannot predict if suspicious calcifications are signs of invasive or noninvasive cancers.

Because calcifications can be the only sign of malignancy, is important to analyze all of the individual calcifications in a cluster. Radiologists should not dismiss a calcification cluster simply because it contains a few round benign-appearing calcifications. DCIS may form some benign-appearing round calcifications by spreading into a round lobule, a development called cancerization of the lobule. This results in a few round or amorphous calcifications mixed in with pleomorphic calcifications. Thus, the presence of a few round benign-appearing calcifications within a cluster does not exclude a diagnosis of cancer. The radiologist should decide to biopsy a cluster based on the worst-looking calcifications in the group.

Calcification Group Shape or Distribution within the Breasts

Calcification distributions that may represent cancer in the ACR BI-RADS® lexicon are those described as clustered or grouped, linear, branching (calcifications in a line that may show branching) (Fig. 3-6), and segmental (Fig. 3-7). Cancer forms in diseased ducts within a breast lobe, or the so-called “sick lobe,” as described by Tot and Gere.

Figure 3-6 A, Schematic of the distribution of calcifications in ductal carcinoma in situ (DCIS). In DCIS, individual calcification forms are linear and branching, and the entire cluster can form a linear or branching shape by following the duct (left). The resulting calcification distribution forms a cluster or a linear or branching pattern on the mammogram (right), depending on where the tumor grows. B, Calcifications growing in a V-shaped linear pattern. Note the oil cyst and other nonspecific calcifications near the DCIS. C, DCIS calcifications growing in a branching pattern. Linear and branching patterns are seen in benign secretory disease on spot magnification (D) and craniocaudal (E) mammograms, but the calcifications are larger and rodlike and branch over a wider area than in the DCIS calcifications shown in parts B and C. F, Pleomorphic DCIS calcifications in many linear clusters over a segmental distribution. Note that the DCIS calcifications are less sharply defined, smaller, and more tightly packed than the secretory disease calcifications. G, Magnification view of part F showing the linear and branching cluster shapes of the DCIS calcifications.

Figure 3-7 Segmental calcification and ductal carcinoma in situ (DCIS). A, When DCIS grows and calcifies in an entire breast duct (left), the resulting calcifications can fill an entire segment (right). B, A cropped mediolateral mammogram shows pleomorphic calcifications in a segmental distribution, a finding indicative of DCIS growing in a duct and its branches. Note the suggestion of tubular soft tissue in ducts associated with the calcified DCIS. C, A craniocaudal mammogram shows DCIS growing in a segmental or regional distribution, a finding indicative of one or two ducts filled with tumor over the entire outer breast quadrant. Note the clustered and scattered pleomorphic calcifications in DCIS (D). E, Schematic of examples of calcification distributions; cluster shapes and segmental calcifications that are usually in cancers versus diffuse or regional calcifications that are usually benign. F to H, Examples of calcification distributions, all representing DCIS. F, Clustered DCIS calcifications with punctate and fine linear forms. G, A wide linear cluster of DCIS pleomorphic calcifications. H, Segmental pleomorphic DCIS calcifications, similar to part A but in a different patient. I, Examples of diffuse or regional calcification distributions, which are usually benign.

Isolated calcification clusters suggest an isolated disease process in a small volume of tissue. This may represent DCIS, invasive cancer, fibrocystic change, papilloma, or sclerosing adenosis. For clusters, one analyzes both the individual calcification forms and the overall cluster shape, which may be a clue to whether the cluster is benign or malignant. Lanyi suggested that the overall cluster shape is especially suspicious if it has a swallowtail, or V, shape, because it suggests cancer in tumor-packed branching ducts. On the other hand, calcifications forming in round clusters may be forming in acini and be benign, especially if the individual calcifications within the cluster are also benign-appearing (see Fig. 3-7E).

The ACR BI-RADS® terms linear branching and segmental describe suspicious findings because they suggest a process within a duct and its branches. The term linear describes calcifications in a line and can represent tumor in a duct or a focal benign process. A segmental distribution is suspicious for cancer because it suggests a process within a branch and its ducts. Segmental calcifications cover slightly less than a quadrant and form in a triangle with its apex pointing at the nipple (see Fig. 3-7F to H).

BI-RADS® terms suggesting benign calcification distributions include regional and diffuse/scattered (see Fig. 3-7I). This pattern suggests innumerable scattered and occasionally clustered calcifications widely dispersed over the breasts and often reflects benign processes, which are also often spread widely throughout both breasts. Calcifications widely distributed in both breasts are usually due to fibrocystic change. Regional calcifications extend over more than one ductal distribution (Box 3-4). Diffuse extensive benign-appearing calcifications in both breasts rarely represent breast cancer. The decision to biopsy calcifications is based on their distribution within the breasts, the worst features of the individual calcification clusters, change over time, the clinical scenario, and common sense.

Number of Calcifications, Calcification Distribution, and Cluster Shape

The number of calcifications in a cluster is as important as the individual calcification shapes. Sigfusson and colleagues reviewed thousands of calcification clusters on mammograms and showed that clusters containing fewer than five calcifications rarely represented cancer on biopsy. Based on this observation, biopsy of these calcification clusters is unlikely to yield cancer. Biopsy of a cluster containing fewer than five calcifications should be undertaken only if the individual calcification forms are extremely suspicious or if the calcifications present themselves within a suspicious clinical scenario.

Sigfusson and colleagues also showed that cancer was more likely with increased numbers of calcifications in the cluster. In clinical practice, calcifications are particularly worrisome if magnification shows many more tiny calcifications than originally suspected on the standard mammogram or if one or more of the calcifications has a linear form.

However, Sigfusson and colleagues also showed that if there were immense numbers of calcifications, and particularly if they were diffusely scattered through the breast, they were most likely benign. Of course, this is true only if the individual calcification shapes are also benign in appearance.

Artifacts Simulating Calcifications

Radiopaque materials on the skin can simulate calcifications. This commonly occurs with deodorant and antiperspirant in the axilla or with radiopaque salves used on dermal skin tags or warts. Sometimes the deodorant or powder will produce dense particles in skin creases, suggesting the diagnosis. If one suspects deodorant artifact, have the patient wash her armpit to remove any deodorant. The deodorant should disappear on repeat films after the armpit has been washed (Fig. 3-8).

Figure 3-8 A, Powder on the skin simulating cancer. A magnification view of the breast shows round tiny calcific particles suggestive of ductal carcinoma in situ, but they were not seen on the orthogonal view. B, A repeat mammogram after wiping the patient’s skin shows no particles, thereby confirming a skin artifact.

Dermal lesions or warts can hide radiopaque salves in their crevices, simulating calcifications in a mass. To distinguish the common dermal lesion from intraparenchymal breast masses, some facilities put radiopaque skin markers on all moles or skin tags. The skin marker on the “mass” distinguishes dermal lesions from masses inside the breast (Fig. 3-9).

Figure 3-9 A, On the mediolateral oblique view, a skin mole covered by a radiopaque ring suggests a nodule. Visual inspection of the patient confirms its dermal location and eliminates the possibility of an intraparenchymal lesion. B, Magnification view of another mole in tangent shows calcification as debris in the interstices of a mole, simulating clustered calcifications in the breast.

To determine whether a calcified “mass” is a skin lesion, the radiologist reviews the patient’s breast history sheet to see if a skin lesion is noted on the breast diagram, then correlates the diagram and the image. A physical examination of the patient to see if a skin lesion is located at expected location of the finding on the mammogram will clear up any questions. If there is still uncertainty if a mass is really a skin lesion, the technologist can place a radiopaque marker over the skin lesion, then repeat the mammogram in the view that raised the question. Or a mammogram can be performed tangential to the skin lesion and marker. In either case, the mammogram should show the marker on a superficial “mass” if it is indeed a skin lesion.

Hair artifacts are white, thin, linear, strandlike opacities near the chest wall (Fig. 3-10) that occur when patients with long hair lean forward for their mammogram. Long hair overlaps into the field of view, causing the artifact. A repeat mammogram with the patient’s hair pulled away from the field of view will eliminate the strandlike artifacts on the mammogram.

Figure 3-10 A, A craniocaudal mammogram shows a strandlike, curvilinear hair artifact near the chest wall over the pectoral muscle. B, After moving the patient’s hair from the field of view, a repeat mammogram shows no hair artifact.

Fingerprints are an artifact seen on SFM. This artifact has a characteristic whorled appearance caused by sticky fingers handling sensitive mammographic films or film-intensifying screens (Fig. 3-11). Sometimes this artifact simulates the linear calcifications in DCIS. A repeat film in the same projection after the screen has been cleaned will have no fingerprints in the same location, thereby resolving the issue.

Figure 3-11 A and B, Whorled curvilinear whitish artifacts on two mammograms from two different patients represent characteristic fingerprints caused by sticky fingers lifting the emulsion off sensitive mammography film.

Round Calcifications (0.5 mm or Less Is Punctate)

Small, 2- to 4-mm round benign intraparenchymal breast calcifications can be seen in any location within the breast. Punctate calcifications form in acini and breast lobules and take on their shape. Punctate calcifications are round, sharply marginated, and densely calcified. Their characteristic appearance suggests a benign diagnosis, and they are often seen in fibrocystic change (Fig. 3-12).

Figure 3-12 Craniocaudal mammograms showing large round benign calcifications. A, Rounded benign intraparenchymal calcifications scattered in the breast. B, Other eggshell-type calcifications may represent calcified dilated ductal structures, clearly uncharacteristic of malignancy.

Calcifications with Radiolucent Centers

Rimlike or eggshell-type calcifications with radiolucent centers are virtually always benign. They are usually round or oval and calcify along their edges, with the radiolucent center appearing darker than the white calcified rim. Small isolated calcifications with radiolucent centers are benign, can form around debris in ducts, and are scattered in the breast tissue.

Radiolucent oil cysts or fat necrosis can form in patients who have sustained trauma or have undergone surgery. The center of oil cysts or fat necrosis is dark and fatty on the mammogram, and calcifies along its edge from saponification. Rimlike calcifications surrounding a radiolucent center of a fatty or oil-like substance suggest an oil cyst (Fig. 3-13). On edge, the curvilinear portion of the oil cyst or fat necrosis looks like a long, thin, curved calcification. En face, in the middle of the oil cyst, the calcifications appear amorphous and sheetlike. Calcified oil cysts distributed diagonally across the breast may be caused by blunt trauma from a seat belt or a steering wheel injury from an automobile accident. In any case, when suspecting fat necrosis the radiologist should look at the old mammogram and history to confirm that trauma or surgery has occurred in that area, and that there was fat in the area where the “calcifying fat necrosis” has now formed.

Figure 3-13 A, A photographically magnified view of an oil cyst shows partial rim calcification around a radiolucent center, with plaquelike calcifications seen en face in the cyst wall. Normal breast tissue can be seen through the oil cyst. B, This oil cyst is more completely calcified along its edge than the example in part A. Note that a discernible radiolucent center is still apparent. Lateral-medial (C) and craniocaudal (D) spot magnification mammograms show a thin rim of calcification around a mostly radiolucent oil cyst. E, This patient had previously undergone biopsy, as shown by a linear metallic skin scar marker, and has multiple eggshell-type calcified oil cysts in the biopsy site from surgical trauma. Note the incidental coarse linear secretory calcifications in the lower right corner.

Dermal Calcifications

Skin calcifications are quite small, about the size of skin pores, are single or clustered, and often (but not always) have a calcific rim surrounding a radiolucent center. These eggshell-type skin calcifications are the same size as the skin pores on the mammograms (Fig. 3-14). This entity deserves special attention because dermal calcifications simulate grouped intraparenchymal calcifications when they have no lucent center, prompting biopsy. Any attempt to needle localize dermal calcifications will result in a dismal failure because the hookwire tip will never project onto the calcifications (because the calcifications are in the skin and not in the breast).

Figure 3-14 A, Photographic magnification shows a typical eggshell-type skin calcification around a radiolucent center near the periphery of the breast. B, Other skin calcifications with radiolucent centers. C, A view tangential to the calcifications in part A confirms their dermal origin.

The radiologist suspects skin calcifications when the calcifications appear in a peripheral location or close to the skin, when other skin calcifications are present, or when they occur at sites where skin touches skin, such as in the axilla, the inframammary fold, or the medial portion of the breast (Box 3-6).

Special tangential views confirm calcifications within the skin and virtually exclude malignancy. To localize skin calcifications easily, the technologist does a “skin calcification study,” which is similar to a needle localization study, but without the needle. To localize the calcifications, the technologist uses a mammographic compression plate that contains perforations or an alphanumeric grid around a hole cut in the compression plate (Fig. 3-15). The technologist positions the breast so that the hole is directly over the skin containing the calcifications; the tangential view will not work if the localizing device is placed over the upper part of the breast in the craniocaudal (CC) view and the calcifications are in the skin on the underside. Therefore, it is important to look at both CC and lateral views to determine which portion of the breast skin contains the calcifications before starting the skin calcification study.

Figure 3-15 A skin calcification study. A, The technologist places a grid coordinate plate on the skin containing the calcifications and takes a mammogram. B, The technologist places a BB at the coordinates identifying the calcifications. C, The technologist takes a mammogram tangential to the BB. The calcifications should be in the skin directly under the BB if they are skin calcifications, as in this case.

To perform the skin calcification study, the radiologist looks at the mammogram after placing the localizing grid over the calcifications and reads the coordinates of the calcifications. While the patient is still in compression, the technologist places a small radiopaque skin marker at these coordinates to superimpose the marker on the calcifications. She repeats the mammogram to make sure that the marker is placed exactly over the calcifications. If the marker is superimposed on the calcifications, it should obscure them on the mammogram and is in the right place. The technologist then takes a mammogram tangential to the skin marker. Dermal calcifications will be in the skin directly under the skin marker. Intraparenchymal calcifications will be within the breast tissue under the marker and not in the skin. This process can take from 10 to 30 minutes, depending on whether the facility performs digital or analog mammography.

Milk of Calcium

Milk of calcium has a classic appearance of sedimented calcifications within tiny benign cysts. Its appearance is pathognomonic on mediolateral and CC mammograms and should be left alone. The calcifications are not fixed to the cyst wall and float around the cyst like fake snow swirling in a snow globe. On the mediolateral mammogram, curvilinear dependently layered milk of calcium settles to the bottom of tiny imperceptible cysts. The layering calcifications are seen as dense, linear, or curvilinear in an upright patient on the lateral view (Fig. 3-16). On the CC projection, the calcifications will have a cloudlike or smudgy appearance like tea leaves in the bottom of a teacup.

Figure 3-16 Milk of calcium in lateral and craniocaudal (CC) views. A, The sedimented calcium particles appear linear on the lateral view. B, En face the calcifications look smudgy on the CC view.

The cysts in microcystic milk of calcium are too small to be seen, and only the characteristic linear appearance of calcifications on the lateral view indicates their presence. Microcystic milk of calcium should be suspected when calcifications plainly seen on the lateral or mediolateral oblique view cannot be seen at all on the CC view or just look like a vague smudge (Fig 3-17). Thus, linear calcifications on the lateral view that disappear on the CC view should suggest milk of calcium, particularly if the calcifications are never found on the CC view after a hard search or even after magnification.

Figure 3-17 A, Mediolateral mammogram with the x-ray beam directed horizontally shows innumerable curvilinear calcifications representing calcium layering dependently in a multitude of tiny, invisible cysts. B, A craniocaudal (CC) view with the x-ray beam directed vertically shows round calcifications. In another example, milk of calcium is evident in the mediolateral (C) and CC (D) projections. These clusters could easily be mistaken for ductal carcinoma in situ without the two orthogonal views to confirm the diagnosis of milk of calcium. E, Schematic drawing of milk of calcium in CC and lateral views. The schematic shows the sedimented calcium particles appearing linear or curvilinear on the lateral view. En face the calcifications look smudgy on the CC view.

In macrocystic milk of calcium, lateral views with the x-ray beam directed horizontally will show both the typical layering semilunar, linear, or curvilinear calcifications in the bottom of the cyst and the cyst itself.

The differential for linear calcifications includes DCIS, which can mimic milk of calcium; both are linear or curvilinear on the lateral and mediolateral views. DCIS can be distinguished from milk of calcium on the CC mammogram. Milk of calcium is amorphous or smudgy on the CC projection whereas DCIS retains a linear shape (Table 3-1).

Table 3-1 Milk of Calcium versus DCIS Calcifications

DCIS, ductal carcinoma in situ.

Even though milk of calcium is typically benign and should not undergo biopsy, unrecognized milk of calcium may be recommended for biopsy by accident. Because milk of calcium changes its shape in varying projections, the biopsy may be stopped if the condition is recognized in time. Patients undergoing stereotactic core biopsy for unrecognized milk of calcium lie prone on the stereotactic table, and the milk of calcium layers dependently in the prone patient. The “linear” calcifications change their position within the microcysts and are parallel (rather than perpendicular) to the chest wall. Calcifications that appear much different on stereotactic views compared to the prebiopsy lateral view and layer dependently on the prone view may suggest milk of calcium, thus precluding the need for biopsy (Fig. 3-18).

Figure 3-18 Microcalcifications recommended for stereotactic biopsy have a curvilinear shape on the mediolateral oblique projection (A) and are so smudgy on the craniocaudal view (B) that they are not recognized as milk of calcium. A stereotactic core biopsy scout film shows characteristic layering of calcifications in the dependent portion of the breast in a prone patient, which is suggestive of the diagnosis of milk of calcium. If a lateral scout view had been obtained, the true nature of the calcifications might have been detected and no biopsy recommended. C, Ultrasound shows milk of calcium in the tiny cysts.

Large Rodlike Calcifications (Plasma Cell Mastitis, Secretory Disease, Duct Ectasia)

Plasma cell mastitis is a benign asymptomatic inflammation of the breast in older women. The inflammation is periductal or intraductal. Periductal inflammation results in dense, sausage-like calcifications with radiolucent centers oriented along the breast ducts and pointing at the nipple. Intraductal inflammation results in calcifications filling the ducts, producing a solid, large rodlike or a thinner, needle-like calcification (Fig. 3-19) oriented along the ducts and pointing toward the nipple. The calcifications usually are quite dense, have sharp margins, line up along the duct like cars in a train, and may be unilateral or bilateral.

Figure 3-19 A, A craniocaudal (CC) mammogram demonstrates nonpalpable rodlike or needle-like and occasionally rounded calcifications in a ductal distribution pointing at the nipple, characteristic of plasma cell mastitis or secretory disease. The calcifications are coarse, quite dense, and easily seen and branch over a large portion of the breast. B, A magnification view of secretory disease shows typical large rodlike calcifications. CC (C) and mediolateral oblique (D) mammograms show a linear form and coarse calcifications of early secretory disease. Unlike ductal carcinoma in situ, secretory disease does not usually have many smaller calcific particles associated with the larger calcifications on magnification views. Note the early vascular calcifications in the upper part of image C. E and F, Two views of secretory disease.

Benign secretory disease, also known as plasma cell mastitis, is a DCIS look-alike. Because benign secretory disease forms in ducts, it also forms linear calcifications like those formed in DCIS (see Fig. 3-4C), but unlike DCIS, the calcifications are due to an inflammatory process either within or around the duct. Thus, benign secretory disease calcifications are large, coarse, and “rodlike”; if periductal, they can be sausage-shaped calcifications with a central lucency. Secretory disease calcifications are so big that they can be seen on the mammogram without a magnifier. On the other hand, DCIS calcifications are much smaller, less dense, and finer than those of secretory disease. DCIS calcifications branch quickly and are tightly packed compared to secretory disease calcifications, which branch widely over the breast and can be separated by centimeters (Table 3-2).

Table 3-2 Plasma Cell Mastitis versus DCIS Calcifications

DCIS, ductal carcinoma in situ.

Occasionally, secretory disease causes an associated spiculated mass that simulates carcinoma, resulting in biopsy. However, most often, the classic features of plasma cell mastitis or secretory disease calcifications on the mammogram are well-recognized as a benign entity that should be left alone.

Coarse or “Popcorn-like” Calcifications (Calcifying Fibroadenomas)

Fibroadenomas most commonly occur between puberty and age 30. They are benign oval or lobulated solid masses equal in density to breast tissue on the mammogram. They occasionally calcify with classic coarse, dense “popcorn-like” features; they should be left alone (Fig. 3-20A). Fibroadenomas are multiple in approximately 10% to 20% of cases and result from epithelial and intraductal proliferation of breast elements. Fibroadenomas have intracanalicular and pericanalicular forms. They are often well-circumscribed, low-density masses that are impossible to distinguish from cysts on the mammogram when they do not calcify.

Figure 3-20 A, A magnification view shows fibroadenoma with a typical “popcorn-like” appearance. B, In another patient, a fibroadenoma appears as dense round calcifications at the edges of the mass. Note the coarse appearance of the calcifications; such an appearance distinguishes fibroadenoma from invasive ductal carcinoma, which would contain fine or pleomorphic calcifications.

Calcifications within a fibroadenoma usually start at its periphery. The calcifications are large and dense, although at an early stage they may be somewhat irregular and small (see Fig. 3-20B). Periodic mammography may show slow progression of the calcifications from the tiny irregular forms to the more classic, dense, popcorn-like appearance, occasionally totally replacing the fibroadenoma with calcium (see Fig. 3-20). If the calcifications are not typical of fibroadenoma or if the mass shape or other features are not characteristic, consideration should be given to needle biopsy to establish a histologic diagnosis. However, fibroadenoma with the classic, characteristic mass shape and typical calcifications should be left alone.

Dystrophic Calcifications

After breast biopsy, linear and amorphous calcifications can form in the surgical bed, occasionally accompanied by fat necrosis, causing pleomorphic and bizarre calcifications. A history of previous surgical biopsy or trauma, when correlated with a surgical scar, should reveal the true nature of these calcifications as dystrophic (Fig. 3-21). Some facilities use a metallic linear scar marker directly on the patient’s skin scar. This helps radiologists correlate the surface skin scar with underlying postbiopsy scarring (Box 3-7). Postbiopsy calcifications developing in a cancer biopsy site deserve special consideration because they may be forming in an in-breast tumor recurrence.

Figure 3-21 A, A mediolateral oblique view shows punctate calcifications in the surgical bed after biopsy and radiation therapy for cancer, with a linear metallic marker over the skin (marker also seen in parts B and C). B, Photographic magnification shows round punctate calcifications in the surgical bed, which were benign on biopsy. C, Recurrent ductal carcinoma in situ in a biopsy site after radiation therapy is shown as seven new clustered calcifications, similar to the benign calcifications seen in part B.

Calcifications in an irradiated breast due to calcifying sutures or benign fat necrosis usually develop 2 years or later after surgery and radiation therapy. Dystrophic calcifications in this setting may be difficult to distinguish from cancer (see Fig. 3-21). In the immediate postoperative period, comparing the current study with the prebiopsy, postbiopsy, and specimen mammograms can help determine whether the calcifications represent unresected tumors missed at the initial surgery, residual benign-appearing calcifications, or new calcifications.

The differential diagnosis for new calcifications in an irradiated cancer biopsy site includes fat necrosis and recurrent cancer. Radiation therapy fails at a rate of about 1% per year, thus resulting in failure rates of about 5% at 5 years and 10% after 10 years. If new calcifications are seen at the biopsy site, and if they are fine, innumerable, pleomorphic, and increasing in number over time, biopsy should be performed to exclude recurrent tumor. Because of the problem of recurrent breast cancer in the cancer biopsy site, biopsy may be required more frequently for benign dystrophic calcifications to confirm or exclude cancer recurrence (versus postsurgical calcification).

A special type of calcification forms after accelerated partial breast irradiation (APBI). Unlike whole-breast radiation, APBI or intraoperative radiation therapy uses more intense radiation over a short period of time on only the biopsy site and a small margin of tissue around it. This is because breast cancer recurrences most often occur in or around the biopsy site. APBI can cause typical round, dense dystrophic calcifications in the biopsy bed that are so dense they almost look like metal.

Vascular Calcifications

Arterial calcification from atherosclerosis has a characteristic appearance of two parallel calcified lines, representing calcification in the arterial wall (Fig. 3-22). Early arterial calcification along vascular walls may simulate the suspicious linear calcifications of DCIS. Seeing a noncalcified vessel leading to the calcifications may establish that the calcifications are in a calcified part of the blood vessel. Magnification views of vascular calcifications will show arterial tram-track calcifications in two parallel lines, with coarse calcifications en face in the vessel wall between them.

Figure 3-22 A, Photographic magnification of easily recognizable dense parallel calcifications along arterial walls. Calcification between the parallel calcific lines represents arterial wall calcifications seen en face. B, The tubelike vascular calcification on the right side of the image is easily distinguished from secretory disease and an early oil cyst. C to E, Vascular calcifications and ductal carcinoma in situ (DCIS). C, Vascular calcifications and five clustered linear calcifications in DCIS. The tram track appearance of the vascular calcifications is easily distinguished from the clustered DCIS calcifications. D, Magnification view of DCIS calcifications shown in part C. E, Vascular calcifications and linear calcifications in DCIS. The tram track vascular calcifications are hard to distinguish from the linear DCIS calcifications.

Calcifications from Foreign Bodies (Silicone Injections, Other)

Classically associated with the injection of silicone or a paraffin-like substance into the breast for purposes of augmentation, foreign-body granulomas in the breast have a characteristic eggshell-type appearance (see Fig. 9-9). The eggshell calcifications are innumerable and are packed closely together where the injection occurred. They are usually a few millimeters in size, but occasionally are larger because of fat necrosis or inflammation; they may have surrounding white fibrotic reaction that causes a palpable mass. Silicone injection calcifications obscure the underlying breast on both mammography and ultrasound, making it difficult to evaluate the breast by physical examination or imaging.

Calcifications can also form in the fibrous capsules around breast implants. These are characteristically dense, dystrophic calcifications that parallel the implant (Fig. 3-23).

Figure 3-23 When a breast implant is removed, the fibrous capsule that forms around the implant is often left in place. The dystrophic calcifications forming in the fibrous capsule are typically seen near the chest wall in the deflated capsule, as shown here. In Figure 9-9, a craniocaudal mammogram shows multiple round tiny eggshell-type calcifications representing calcification around silicone injection granulomas. Silicone and other substances were injected directly into the breast for augmentation in Southeast Asia, but they cause dense calcifications. Direct injections of silicone are easily distinguished from dystrophic calcifications in the implant capsule after implant removal, shown here.

Objects inserted into the breast cause other foreign-body granulomas or can be seen because they are radiopaque. Foreign objects can be recognized by reading the patient history and by noting the foreign body shape.

Stability of Pleomorphic Calcifications

In general, stability of calcifications over time on several mammograms indicates that the calcifications are benign. However, the stability of pleomorphic calcifications does not indicate they are benign. Although it is true that calcifications in cancer are usually new or increase over time, suspicious pleomorphic calcifications in cancer can be stable.

A study by Lev-Toaff and colleagues looked at old mammograms of suspicious calcifications that were biopsied and shown to be DCIS or invasive ductal cancer to see how long the calcifications were present and if they had changed at all. They showed that the malignant-appearing calcifications were stable over a 6- to 50-month period. If the calcifications were present previously and changed, they were more likely to be associated with invasive cancer than with DCIS. These findings indicate that suspicious pleomorphic calcifications may represent DCIS or invasive ductal cancer even if they are stable and that biopsy should be performed on any suspicious pleomorphic calcifications.

Ultrasound in Evaluation of Calcifications

Scientific studies show that high-resolution ultrasound can detect calcifications in the breast or find the masses that have caused the calcifications. Often, however, the normal background speckle of breast parenchyma on ultrasound masks calcifications, if the calcifications alone are the only finding and there is no mass associated with them. Some investigators suggest that ultrasound scans in the region of calcifications are helpful if the scan shows a suspicious mass representing invasive ductal cancer or if it pinpoints the calcifications for percutaneous biopsy or needle localization (Fig. 3-31).

Figure 3-31 Calcifications on ultrasound. The role of ultrasound in detecting calcifications is controversial, but it may be helpful if the scan shows a mass in a location known to have calcifications. A, Mammography shows suspicious clustered pleomorphic calcifications in a patient with Paget disease of the nipple. B, Hypoechoic, irregular mass containing calcifications. Pathologic examination showed invasive lobular and ductal cancer and ductal carcinoma in situ with calcifications.