Osteoid Osteoma and Osteoblastoma

Osteoid osteoma arising in an intra-articular location is relatively uncommon; however, it may occur in the region of the elbow. It is relatively common at the elbow, but only a few reports on the presentation,³⁶ diagnosis,³³ and management⁴¹ have appeared. This small benign bone tumor occurs in patients of any age, most commonly children and young adults. As with most bone tumors, boys and men are more commonly affected than girls and women. Unremitting pain is the usual symptom for which the patient seeks medical attention; however, progressive loss of motion may also be a characteristic feature. Pain during the night is particularly prominent. Aspirin may afford very dramatic relief of pain, a fact that may even suggest the diagnosis of osteoid osteoma. Occasionally, the pain may be experienced at a site remote from the lesion. Another peculiar feature of this tumor is its occasional association with atrophy of the adjacent soft tissues. In the Mayo Clinic’s experience with 14 such cases, eight have occurred in the distal humerus, four in the ulna (two coronoid, two olecranon), and two in the radial head–neck region⁶⁰ (Fig. 82-2).

FIGURE 82-2 Distribution of 14 osteoid osteomas treated at the Mayo Clinic.

As noted previously, when osteoid osteoma occurs at or near the elbow joint, there is characteristically loss of some flexion or extension, but pronation and supination are preserved. In addition, there may be a synovial reaction that may further confuse the diagnosis. The most striking feature of these tumors is the prolonged average time required for making the diagnosis. In the Mayo Clinic’s experience, the delay to diagnosis averaged almost 2 years.⁶⁰

The osteoid osteoma, by definition, is small, usually no more than 1.5 cm in diameter. Lesions that are clinically and histologically similar but are 2 cm or more in diameter are referred to as osteoblastomas; these lesions have clinical features somewhat different from those of osteoid osteoma,⁴⁸ but loss of motion is a common feature.^8,27 Osteoid osteoma is small when first encountered and remains small,³⁰ further complicating the diagnosis.

An extensive diagnostic evaluation is usually required in determining the precise location of the osteoid osteoma.^12,34 When the patient complains of unremitting pain in the elbow, plain radiographs are obtained (Fig. 82-3). These may or may not reveal the presence of the tumor. The lesion typically appears as a central small nidus, which is a radiolucent area usually surrounded by an area of sclerosis. It is this sclerosis that is usually seen³⁸; the central area of the nidus is more difficult to identify. When the lesion is located on the surface of the bone, there may be periosteal new bone formation thatfurther obscures the nidus.³⁶ Cronemeyer and colleagues¹³ described an unusual radiographic feature of osteoid osteoma in the elbow joint—subperiosteal new bone formation in adjacent bones; for example, an osteoid osteoma in the distal end of the humerus that exhibits periosteal new bone formation in the proximal radius and ulna.¹³ These authors concluded that “awareness of this association will prevent misdiagnosis of the benign neoplasm as an inflammatory arthritis.”

FIGURE 82-3 Osteoid osteoma in a 10-year-old boy, upper radial shaft. Rarefied nidus with central sclerotic area and surrounding bone formation (arrow).

Technetium-99m scintigraphy has been helpful in locating these lesions.³³ If technetium-99m scintigraphy reveals no abnormality, an osteoid osteoma is unlikely; however, if the bone scan is positive, further diagnostic studies of the involved area should be undertaken (Fig. 82-4). If there is any significant synovial reaction, there may be increased uptake owing to the synovitis as well as to the lesion itself.^51,52 Sometimes, multiple radiographs must be taken before the lesion can be identified. Today, CT is the diagnostic standard, however, if the tumor is so small it may be missed on this examination.⁵⁵

FIGURE 82-4 Patient presented with a chronic painful elbow of almost 1 year’s duration. A, Plain film was read as negative, although a generalized increased density of the olecranon might be appreciated. B, Technetium bone scan indicates intense uptake in the olecranon region. C, The patient was found to have an osteoid osteoma in the coronoid portion of the proximal ulna.

Grossly, there is usually some sclerotic bone surrounding a central nidus. This nidus may be somewhat redder than the surrounding cortical bone and has been described as having the appearance of a small cherry. It is sometimes helpful to obtain radiographs of the excised block of tissue before the pathologist cuts into the block. Microscopic examination of the surrounding bone shows no unusual features; the nidus itself consists of a network of osteoid trabeculae (see Fig. 82-3).

Osteochondroma

Osteochondroma is probably the most common benign bone tumor, but it is not very commonly encountered in the elbow. The incidence may be somewhat higher than that reflected in our surgical experience, however, because many osteochondromas in other locations are asymptomatic and presumably may also be in the region of the elbow. The osteochondroma is not inherently painful but causes symptoms by pressure on adjacent structures. The tumor may be found in a patient of any age, but it usually stops growing when skeletal maturity is reached. An osteochondroma may arise from the surface of any bone but most commonly does so in the metaphyseal region of long bones (Fig. 82-5). The tumor tends to project away from the joint along the direction of attached muscles. The tumor may be pedunculated on a stalk or may be sessile and have a broad base (Fig. 82-6). The tumor is covered by a cartilage cap, which, if it becomes markedly thickened, suggests the possibility of sarcomatous transformation. If it is more than 1 cm thick, the risk of secondary chondrosarcoma is relatively high. In children, the cartilage cap is normally thicker than in adults. Probably fewer than 1% of osteochondromas ever become malignant.²⁹

FIGURE 82-5 Osteochondroma in a 23-year-old woman. Radial shaft with cortical and medullary bone extending into tumor.

FIGURE 82-6 Osteochondroma of the distal humerus in a 41-year-old man. Note the soft tissue reaction.

Multiple osteochondromas sometimes occur, a condition that tends to be familial. When multiple bones are involved, there may be some element of dysplasia with the deformity and the elbow can be severely involved. Because of the possibility of sarcomatous change, probably near 10%, patients with multiple osteochondromas need to be carefully observed through periodic follow-up examination.

Osteochondromas in the region of the elbow may cause mechanical difficulties; specifically, interference with the motion of the elbow joint. In addition, the cartilage cap may impinge on important neurovascular structures. If there are symptoms or mechanical or cosmetic difficulties, complete excision of the osteochondroma, together with the overlying cartilage cap, is performed. Excision commonly involves the use of an osteotome to shave the lesion level with the underlying cortical bone. Such simple excision generally results in cure, although local recurrence may occasionally be noted, indicating that part of the cartilaginous cap was left behind. If the cap is thicker than 1 cm in an adult, the lesion must be carefully studied histologically to exclude the possibility of a sarcoma.

Giant Cell Tumor

Benign giant cell tumors are occasionally encountered in the region of the elbow. In general, giant cell tumors more commonly affect women than men, contrary to the situation with most benign and malignant bone tumors. About 80% of giant cell tumors occur in persons who are older than 20 years of age. This point may be helpful in differentiating a giant cell tumor from an aneurysmal bone cyst, which may be radiographically similar but tends to occur in persons who are younger than 20 years of age.

Giant cell tumors nearly always occur in the epiphyseal region and may extend to the articular surface of the bone. Campanacci and coworkers¹⁰ have attempted to grade giant cell tumors according to radiographic criteria; thus, grade 1 lesions are radiographically indolent, and grade 3 tumors are radiographically aggressive. Unfortunately, the majority of giant cell tumors are probably what Campanacci and colleagues refer to as grade 2, in which the radiographic appearance is aggressive but the tumor has not yet broken through cortical bone. Radiographic grading may be important in helping the surgeon decide on the appropriate treatment.

Grossly, the tumor consists of a red, soft tissue that typically extends up the subchondral bone at the articular surface. Microscopically, a giant cell tumor shows a combination of giant cells and mononuclear cells, with a more or less uniform distribution of the giant cells. Giant cell tumors that appear to be more aggressive histologically do not necessarily behave more aggressively clinically.¹⁷

The extent of surgery required to eradicate giant cell tumors is somewhat controversial. In the region of the elbow, particularly difficult problems may be encountered. The distal end of the humerus does not lend itself well to surgical excision by curettage unless the lesion is radiographically a grade 1 lesion. Total excision of the distal end of the humerus, although it would probably be curative and prevent local recurrence, creates a very serious problem for the reconstructive surgeon. Allograft replacement might be considered in this setting, but the decision about the method of treatment is often exceedingly difficult. Excision by curettage in other locations results in a local recurrence rate of approximately 25%. It is probably reasonable to accept this risk and to try curettage for the first treatment because the alternative of resection of the distal end of the humerus is so drastic (Fig. 82-7). However, if the tumor has already broken through the cortex into the surrounding soft structures, curettage is unlikely to be effective. For tumors of the proximal end of the ulna, curettage might be more reasonable because there is more bone to work with; hence, a larger margin of normal bone can be included in the resected specimen, whether resection is done by curettage or actual excision. Whenever possible, the treatment of choice is to pack the tumor cavity with methylmethacrylate (Fig. 82-8). This method of reconstruction has, in other locations, proved to be effective. If the proximal radial head is involved with a reasonably small tumor, it is probably best treated with simple excision.^28,32

FIGURE 82-7 A, Gross destruction of the distal humerus due to a locally aggressive giant cell tumor. The patient was treated by resection of the distal humerus and replacement with joint replacement arthroplasty. B, The arc of motion is 15 to 140 degrees with no pain, and there is no evidence of implant loosening at 3 years.

FIGURE 82-8 Giant cell tumor involving the lateral condyle in a 25-year-old patient. The lesion was curetted, and the defect was filled with methylmethacrylate.

Radiation therapy for benign giant cell tumors should be avoided, if possible. In our previous experience, irradiation of benign giant cell tumors was accompanied by a significant risk of subsequent malignant transformation.

Aneurysmal Bone Cyst

An aneurysmal bone cyst typically contains abundant benign giant cells in scattered zones and formerly was included among the giant cell tumors. It is different, however, because it nearly always contains blood-filled spaces, is somewhat fibrogenic, and usually has zones with osteoid formation and trabeculae of bone.

An aneurysmal bone cyst may arise de novo, or a similar reactive change may be seen in various benign and even in malignant tumors of bone. It is necessary to rule out any associated pathology, because the clinical behavior of the lesion depends on the nature of the underlying pathology.

In the Mayo Clinic’s experience with 134 aneurysmal bone cysts unrelated to pre-existing disease, 43% occurred in men. In contrast to the age of predilection for giant cell tumors, 78% of the patients were younger than 20 years of age. Only eight examples of aneurysmal bone cysts were found in the region of the elbow. Pain and swelling are the most common features.¹⁴

Radiographically, the diseased area is sometimes confusingly like that of a malignant tumor, but the zone of rarefaction is usually well circumscribed, eccentric, and associated with an obvious soft tissue extension of the process (Fig. 82-9). Classically, the soft tissue extension is produced by bulging of the periosteum and a resultant layer of radiographically visible new bone that delimits the periphery of the tumor. Fusiform expansion may be produced, especially when small bones such as a fibula or a rib are affected. The lesion is usually metaphyseal in location.^6,18

FIGURE 82-9 Aneurysmal bone cyst of the ulna in a 5-year-old boy. Note circumscription of the mass, which is associated with destruction of the shaft and the end of the bone.

Pathologically, an aneurysmal bone cyst contains anastomosing cavernous spaces that usually constitute the bulk of the lesion. The spaces are usually filled with unclotted blood, which may well up into, but does not spurt from, the tumor when it is unroofed. The most important factor to recognize histologically is the benign quality of the constituent cells.^16,46 Telangiectatic osteosarcomamay simulate aneurysmal bone cyst when viewed at low magnification.

Treatment is essentially the same as that for benign giant cell tumors. Curettage and bone grafting are usually required, and the majority of lesions treated in this way will be cured. Perhaps 25% of these cases will recur and require additional surgery.

Lymphoma

Currently, the term malignant lymphoma is used for those small round cell tumors of bone that previously were referred to as reticulum cell sarcoma.⁴² Lymphoma tends to occur in middle-aged or elderly adults; young persons are uncommonly affected. Patients with lymphoma generally present with pain and perhaps swelling in the region of the lesion. The tumor may arise primarily in any bone, including bones in the region of the elbow (Fig. 82-15).

FIGURE 82-15 Radiograph of assumed “avascular necrosis” of distal humerus (A); lymphoma found eroding the posterior portion of the trochlea was excised (B).

The radiographic features of lymphoma are nonspecific (Fig. 82-16). There is usually a diffuse, destructive, mottled appearance with indistinct margins. Variable degrees of sclerosis may be present in the lesion; the cortical bone is usually eroded, and the tumor may extend into the adjacent soft tissues. Periosteal new bone formation usually is not a prominent feature.

FIGURE 82-16 Malignant lymphoma producing malignant-appearing destruction of the distal part of the humerus in a 60-year-old woman.

Grossly, lymphoma tissue is usually gray or white and very soft. Microscopically, malignant lymphomas fit into the group of small round cell tumors. Under low power, the tumor shows a permeative pattern. The infiltrate tends to fill up the marrow cavity without destroying medullary bone. When a diagnosis of lymphoma in bone is made, it is important to stage the disease process. If the disease is localized to one site, the prognosis is excellent.⁴⁰ About a fourth of patients will have multiple bones involved. Even these patients do well. However, if there are other sites, such as liver, spleen, or lymph nodes, the survival rate decreases dramatically.

Lymphoma is generally treated with radiation therapy if there is only a solitary lesion of bone. For lymphoma in the region of the elbow joint, some morbidity can probably be expected from the radiation therapy. Radiation therapists generally try to avoid circumferential treatment of an extremity to allow some normal lymphatic channels to remain open. Failure to do so may result in significant swelling distal to the treatment area. It may be difficult or impossible to avoid treating the entire circumference of the extremity in the region of the elbow. In addition, when radiation exceeds approximately 4000 rad, radiation therapists generally try to direct treatment away from the articular surface.

There is no clear-cut or obvious advantage to the use of adjunctive chemotherapy at the time of initial treatment if only a solitary lesion is present.⁴⁹

In general, lymphoma presenting primarily in bone has a long-term survival of about 60%.⁷ However, no figures are available for the occurrence of lymphoma of bone specifically at the elbow.

Ewing’s Sarcoma

Ewing’s sarcoma may arise in any bone, including those in the region of the elbow. Ewing’s sarcoma is more frequently found in children than adults; very young infants, however, very rarely have this tumor.

The usual radiographic appearance of Ewing’s sarcoma is that of a mottled or moth-eaten destructive lesion that may contain both lytic and blastic areas (Fig. 82-17). Although not pathognomonic, there is frequently periosteal reactive new bone, which may form layers, forming the “onion skin” appearance that is reported to be typical of this disease. The radiographic appearance combined with the presence of fever and an elevated erythrocyte sedimentation rate may lead to the erroneous diagnosis of osteomyelitis.²

FIGURE 82-17 Recurrent Ewing’s sarcoma with a cyst-like lesion of the upper half of the ulna in a 21-year-old woman. The original tumor had been treated 10 years previously.

Grossly, Ewing’s sarcoma may be very soft or even semiliquid; indeed, the appearance may simulate the purulence of infection. Microscopically, Ewing’s sarcoma is very cellular, composed of small round cells that are remarkably similar to one another. Periosteal new bone formation, if present, may complicate the histologic interpretation.⁴⁷

Treatment of Ewing’s sarcoma of bone in the region of the elbow is similar to that for other sites. The local lesion is generally treated with radiation therapy, and systemic combination chemotherapy is generally used in an attempt to prevent micrometastases. Although there is a growing trend toward considering a larger role for surgery in the treatment of the primary lesion, there is little enthusiasm for resecting malignant tumors in the region of the elbow because it is difficult to achieve adequate margins in this region without damaging important normal structures.⁴⁴ Even if an adequate resection could be achieved, satisfactory reconstruction would be difficult or impossible. This is particularly true when one deals with children with open physes. Thetreatment for Ewing’s sarcoma is the same as that for lymphoma in the region of the elbow.^5,31 A major side effect is soft tissue fibrosis causing a stiff joint.

Osteosarcoma

Osteosarcoma is the most common bone malignancy except for myeloma. Radiographically, osteosarcoma usually appears to be aggressive, with evidence of cortical destruction and reactive periosteal new bone for-mation. In the distal humerus, the classic “sunburst” appearance may be evident. The precise extent of the lesion may not be apparent on plain radiographs (Fig. 82-18). The tumor can usually be more accurately assessed with a technetium or gallium bone scan. Other studies, such as CT, may be used to help determine the extent of soft tissue involvement if it is present. Magnetic resonance imaging may be helpful in further defining both the extent of soft tissue involvement and the extent of intramedullary involvement.

FIGURE 82-18 Grade 4 osteosarcoma of the distal end of the humerus in a patient with Paget’s disease of the entire bone.

The reactive new bone formation at the periphery of the lesion should not be sampled for biopsy because this will simply lead to confusion in the interpretation of the histologic findings. If there is a soft tissue extension of the tumor, this is the area that is best to biopsy because it is usually the most malignant and the easiest to process in the pathology laboratory.

About one half of these tumors are predominantly fibrous or cartilaginous, and the remainder are predominantly bone forming. Because any one of these three types of differentiation may predominate, the lesions may be subtyped into fibroblastic, chondroblastic, or osteoblastic osteosarcoma. This subclassification may be important because the osteoblastic subtype appears to have a worse prognosis than the other two subtypes.^{9,15,19,35,56–58}

Malignant fibrous histiocytoma can also show areas of matrix production.²⁰ Yet, only one of the 83 tumors listed as malignant fibrous histiocytoma in the Mayo Clinic files occurred in the elbow region. From a practical standpoint, the clinical management of this malignancy is essentially identical with that of osteosarcoma (Fig. 82-19). In the author’s own experience, 8% to 10% of patients with newly diagnosed osteosarcoma are foundto have metastatic disease, either by plain radiography or CT.⁵³

FIGURE 82-19 Grade 4 malignant fibrous histiocytoma producing malignant-appearing destruction of the upper part of the ulna in a 45-year-old man.

The usual treatment of osteosarcoma, as of other radioresistant malignant bone tumors, is surgical ablation. For many years, amputation was required. However, today the majority of patients with osteosarcoma can be managed with various limb salvage procedures. Neoadjuvant chemotherapy is generally employed before one proceeds with surgery, and additional chemotherapy is usually offered after surgery. The prognosis for patients with osteosarcoma today is much improved; 70% to 90% of such patients may be long-term survivors.

Lipoma

Lipoma is probably the most frequently encountered benign soft tissue neoplasm and is the most common tumor in the elbow region. It is usually solitary, but multiple lipomas have occurred. The tumor is simply a localized collection of adipose tissue that is histologically and chemically similar to ordinary fat.

Most lipomas are small, asymptomatic, and relatively dormant in that they seem to remain approximately the same size. Occasionally, however, the tumor may grow and become symptomatic. If there is trauma to the area, necrosis may develop within the lipoma, and this is usually symptomatic. Most lipomas consist almost entirely of adipose tissue; however, there may be increased vascularity, in which case the lesion is referred to as angiolipoma.²¹

Most of these lesions can be easily and confidently diagnosed on the basis of the clinical examination alone; however, some lipomas may not have the clinical characteristics of the usual subcutaneous lipoma and may require further diagnostic modalities.

Surgical excision should be considered for lipomas that increase in size, are symptomatic or cosmetically undesirable, or interfere with function and in situations when the diagnosis is not certain (Fig. 82-21). For most such tumors, a simple marginal excision is all that is indicated. The vulnerability of the neurovascular structures is of particular concern for lipoma of the antecubital space. When a lipoma is located within the belly of a muscle, it may be necessary to sacrifice some normal muscle tissue on all aspects to minimize the risk of local recurrence. At the elbow, this can cause permanent stiffness.

FIGURE 82-21 Expanding, prominent soft tissue mass in the cubital space (A) was found to be a benign lipoma (B).

Glioma

The editor has encountered an instance of a glioma in the anticubital space. Diagnosis was delayed 2 years, although the pain was “unbearable.” Complete relief of symptoms was effected with resection.

Ganglion

A ganglion is a cystic lesion generally found in the hands, wrists, and feet, but it may be found less commonly in the region of the elbow. A true ganglion has no or only a poorly defined synovial lining. Although the ganglion may connect with the joint, it does not always do so; indeed, the lesion may occur within a tendon, in a muscle, or even on occasion in bone. Treatment is simple excision, ensuring that the entire lesion has been removed and, as with the lipoma, that the neurovascular elements are carefully protected. Not all ganglia require excision, however, and most patients may be treated symptomatically.

Myxoma

A myxoma occasionally occurs in the soft tissues at the elbow. This lesion is soft, well circumscribed, and myxoidal. Histologically, the lesion is hypocellular and contains stellate cells in a myxoid stream. A myxoma is relatively small and is usually encountered in the superficial soft tissues. It is not uncommon for this tumor to arise within the substance of a major muscle.

The treatment for myxoma is excision; however, a wide excision, rather than a marginal resection, is probably indicated because this tumor tends to recur if it is marginally excised.

Pigmented Villonodular Synovitis

In the past, pigmented villonodular synovitis had various names, including xanthoma, xanthogranuloma, giant cell tumor of the tendon sheath, and myeloplaxoma. This disease probably belongs in the middle of the spectrum of diseases, within the general category of fibrous histiocytoma. It involves the synovium, bursae, or tendon sheaths. The knee is the most common site of involvement. In the authors’ experience, only two cases occurred in the elbow joint.⁴³ This is not surprising, because Pimpalnerkar⁴³ reports that only 18 cases have been cited in the literature through 1998.

Clinically, there are two forms of the disease: nodular and diffuse. The nodular or localized form is probably most frequently encountered in the small joints of the fingers, whereas the diffuse form is most commonly found in the knee joint. At the elbow, swelling, with a suggestion of increased thickening of the synovium, may be present, but motion loss is always present. Radiographs may reveal cystic erosions on either side of the joint (Fig. 82-22). When erosions are found and there is no loss of joint space and no demineralization of the surrounding bone, the diagnosis should be suspected. In most cases of pigmented villonodular synovitis, however, there is no bony erosion but there is evidence of lobular swelling of the soft tissues.⁴

FIGURE 82-22 Pigmented villonodular synovitis in a 17-year-old girl, with a 3-year history of pain and swelling. Note cystic erosions.

Microscopic study shows a stromal background of reticulin and collagen fibers, in which various different cells may be found. The firm, nodular lesions have more collagenous stroma, whereas the soft villous lesions have less stroma.

In the nodular form, the nodule may be simply excised with the expectation that a cure will be achieved in most cases. However, the results of treatment of the diffuse form are likely to be followed by local recurrence, which is more frequent when there is evidence of bony erosion. Even multiple synovectomies have not always been curative; because of this, various alternative treatments have been attempted. Radiation therapy has been used, but there is no convincing evidence that such treatment will actually eliminate the disease and prevent local recurrences. High doses of radiation are avoided at the elbow joint. Synovectomy is the treatment of choice, but the incidence of recurrence is at least 33% with open procedure.⁴³ This may be less with arthroscopic procedures (Fig. 82-23). If synovectomy leads to symptomatic local recurrence, arthrodesis is considered in most joints. At the elbow, however, because this joint does poorly with an arthrodesis, replacement arthroplasty would appear to be the treatment of choice.

FIGURE 82-23 Arthroscopic synovectomy is now the treatment of choice for pigmented villonodular synovitis.

Synovial Chondromatosis

Chondromatosis is a benign, tumorous, multifocal, chondromatous, or chondro-osseous metaplastic proliferation involving the subsynovial connective tissue of joints, tendon sheaths, or bursae (see Chapter 83). The process can involve any joint. The average age of the patients is about 40 years; men are affected more often than women. Symptoms include pain and limited motion. The duration of symptoms may be long or relatively short before diagnosis is made. In the Mayo Clinic series, only two thirds of the radiographs showed radiopaque masses (Fig. 82-24).³⁷ Diagnosis is difficult because the radiograph may not reveal ossified bodies even when they are present.

FIGURE 82-24 Synovial chondromatosis of the elbow. Note that a small mineralized focus is evident in the antecubital fossa.

When the radiographic diagnosis is indefinite and symptoms persist without any other obvious cause, diagnostic arthrotomy or arthroscopy is indicated. Because osteochondromatosis may be sharply localized and may not be a diffuse condition of the entire synovium, careful inspection of the whole synovial lining is important. Generally, diagnosis can be made by the gross appearance and confirmed by biopsy. Grossly, nodules of cartilage of varying sizes are seen embedded in the synovium that may be markedly thickened. Histologically, nodules of cartilage are found within the synovium. The authors have seen one example of synovial chondromatosis of the elbow undergo malignant change to chondrosarcoma.

The treatment of osteochondromatosis consists of removing any loose osteochondromatous bodies and the involved synovium from which they arise. In general, complete synovectomy is necessary and today is done arthroscopically. The condition may recur because nests of synovium may be left behind. If this happens, a second procedure, maybe even an arthrotomy, is necessary. Long-standing synovial osteochondromatosis creates secondary osteoarthritis (see Chapters 83 and 85).

Myositis Ossifications (Heterotopic or Ectopic Ossification)

Heterotopic ossification, often erroneously called myositis ossificans, may occur near the elbow, either in muscle or in other soft tissue. In its early, or “florid,” stage, there may be such pronounced cellular activity that it may be mistaken for sarcoma.¹ The relative rarity of this disease has delayed understanding of the peculiar tissue reaction associated with it. The topic has been thoroughly reviewed in Chapter 31.

A similar non-neoplastic benign, reactive process may occur in the deeper portions of the skin. The poorly defined small mass that is found may also show prominent mitotic activity. The lesion is called proliferative fasciitis and has been mistaken for entities such as liposarcoma or fibrosarcoma.¹¹ The rapidly proliferating cells again do not show true anaplasia. Another related entity is proliferative myositis.²⁵ In this condition, there is a tumefactive, intramuscular proliferation of benign fibroblastic cells, but no discernible osseous metaplasia. Mitotic activity may be pronounced, making it possible to mistake this lesion for a malignant tumor.

Synovial Sarcoma

Synovial sarcoma, or synovioma, is a malignant soft tissue tumor that usually arises in the extremities or limb girdles; about 70% of lesions involve the lower extremity, most commonly the thigh, but this tumor does occur in the region of the elbow. In the Mayo Clinic experience, only the tumors of about 20% of patients had suggestive evidence of origin from anatomic synovium.⁶¹ This tumor can be found in patients of any age, but young or middle-aged adults seem to be most commonly affected.

Symptoms may be present for many years before diagnosis. In the Mayo Clinic experience, the average duration of symptoms before diagnosis was 2½ years. The radiographic examination may be particularly helpful because about a third of patients with synovial sarcoma show evidence of calcification. When calcification is found in a soft tissue tumor, synovial sarcoma should be included in the differential diagnosis. This tumor can invade the bone on a rare occasion.³⁹

The tumor is lobular, circumscribed, and gray and may contain areas of calcification, hemorrhage, necrosis, or cyst formation. Classically, synovial sarcoma has a bimorphic histologic pattern; that is, a combination of slender spindle cells and larger epithelial-appearing cells that may form glands or even show squamous change.

Close cooperation between the pathologist and the surgeon is essential if the diagnosis is to be made at surgery. Local excision of the tumor generally results in a local recurrence; with local recurrence, the prognosis for survival is lessened. In the Mayo Clinic experience, the overall 5-year survival rate was 23%, with a median survival time of 39 months.⁵⁹ However, for patients treated after 1960, the 5-year survival rate has been 55% and the 10-year rate has been 38%. Patients who had the best prognosis were those treated with wide excision or radical surgery. Today, the authors usually combine radiation therapy and surgery; with this approach local recurrence occurs in only about 5% of cases. We do not routinely employ lymphadenectomy unless the regional nodes are clinically involved.

Liposarcoma

The pathologic diagnosis of liposarcoma may be difficult, especially when the lesion is histologically of low grade. A lipoma that shows evidence of growth should be suspected of being malignant. Roentgenograms are not as diagnostic for liposarcoma as they are for lipoma, but the combination of more dense and less dense tissues may be characteristic of liposarcoma. CT is very helpful not only in defining the extent of the lesion but also in showing relative densities. Histologically, lipo-sarcomas are recognized because of their component of malignant lipoblasts.

Liposarcomas may arise in any part of the body and are occasionally found at the elbow. Older adults are more commonly affected than younger persons.

The extent of treatment depends, at least in part, on both the size and the grade of the tumor. Lesions that are grade 1 or grade 2 probably can be safely excised with a margin of normal tissue on all aspects, but this can be very difficult at the elbow. If the lesion recurs, it can probably be excised without the need for radical surgery. However, the higher grade lesion should probably be treated with wide resection and perhaps with radical resection unless the tumor can be totally and widely removed without sacrifice of limb function. This is difficult to do with tumors in the region of the elbow, and amputation may be necessary. As with other soft tissue sarcomas, the authors usually combine radiation therapy and surgery. In the Mayo Clinic experience, more than 50% of all patients treated for liposarcoma may expect to survive for 5 years and be free from evidence of disease progression.⁴⁵

Malignant Fibrous Histiocytoma

Malignant fibrous histiocytoma is now the most commonly encountered malignant soft tissue tumor of the extremities and, as noted earlier, may also occur in the bone. The upper extremity and, more specifically, the region of the elbow are not uncommonly affected by this tumor. This tumor can arise in any age group. As with other malignant soft tissue tumors, there are no unique clinical or radiographic features characteristic of this lesion. Both CT and magnetic resonance imaging have been used to define the extent and relationship of the tumor with surrounding structures.

Grossly, this tumor is usually soft and pink or yellow. It may vary in consistency and color from patient to patient and, indeed, even in different areas of the same tumor. There may also be an area of firm, white tumor adjacent to a yellow, mucoid, necrotic area. Tumors arising in the upper extremity in general tend to be smaller than those arising in the buttock or lower extremity, probably because they are noticed by the patient earlier in their evolution. Microscopically, the lesion may vary from the most benign-appearing spindle cells with small nuclei and relatively few mitotic figures, such as those seen in a grade 1 lesion, to the wildly anaplastic, bizarre histiocytic cells found in grade 4 lesions. There is growing evidence that the grade of the lesion as manifested by anaplasia is a more important predictor of behavior than are the histologic subtypes.

There is no one universally acceptable treatment for this lesion. Relatively small tumors may be excised with a margin of normal tissue on all aspects. Larger lesions or those that are histologically higher grade require a more aggressive approach. In this situation, the authors now favor a course of preoperative radiation therapy using approximately 5000 rad, followed after several weeks by excision of the lesion with a margin of normal tissue on all aspects. Adjunctive chemotherapy has not been helpful in our experience.

Epithelioid Sarcoma

Epithelioid sarcoma is a rare, slowly growing malignant tumor that usually begins in the superficial tissues of the hand or forearm and may occur at the elbow. The tumor is made up of small, poorly defined tumor nodules composed of epithelioid cells or histiocytic aggregates. Sometimes, central necrosis in these aggregates of cells suggests that the disease is a granulomatous infection. There is often a delay in recognition of the malignant nature of the disease, and the long-term prognosis for life is poor. Rarely, the tumor erodes into underlying bones (Figs. 82-25 and 82-26). Lymphatic or hematogenous metastasis is common, especially in the later stages of this disease.

FIGURE 82-25 A and B, Epithelioid sarcoma that has eroded into and destroyed much of the distal part of the humerus in a 27-year-old woman.

FIGURE 82-26 Another epithelioid sarcoma that has caused osseous destruction at the elbow.

Treatment for cure requires wide excision. Marginal or intralesional excision almost always results in tumor recurrence and subsequent disease progression. The relatively slow growth of the tumor and the unusual nature of the histology may tend to dissuade the surgeon from performing adequate surgery.