Advantages of and Evidence for Dermoscopy

In two separate meta-analyses, dermoscopy had significantly higher discriminating power than clinical examination for experienced users.^1–3 It is intuitively obvious that this improved diagnostic accuracy translates into improved patient management. For example, in one study, the malignant-to-benign ratio improved in dermoscopy users from 1 : 18 to 1 : 4.⁴

Primary care physicians (PCPs) who were given a 1-day training course in skin cancer detection and dermoscopic evaluation were able to improve their sensitivity for melanoma diagnosis. The study randomly assigned PCPs to the dermoscopy evaluation arm or the naked-eye (no dermoscopy) evaluation arm. The study showed that 23 malignant skin tumors were missed by PCPs performing naked-eye observation, whereas only 6 were missed by PCPs using dermoscopy (P = 0.002). The authors concluded that the use of dermoscopy improves the ability of PCPs to triage lesions suggestive of skin cancer without increasing the number of unnecessary expert consultations.⁵

Dermoscopy can help in the following ways:

Equipment

Dermoscopes illuminate the skin via the use of light emitting diode (LED) lights with or without the use of polarizing filters. Although most units are either nonpolarized (no polarizing filters in place) or polarized (polarized filters used), a few newer units, known as hybrids, allow the operator to toggle between polarized and nonpolarized light within the same unit. Nonpolarized dermoscopes (NPDs) are manufactured by Heine and Welch Allyn (Figure 32-1A). 3Gen manufactures NPDs, polarized dermoscopes (PDs), and hybrid dermoscopes (Figure 32-1B). A number of new dermoscopes attach to smart phones for easy dermoscopic photography.

Figure 32-1 (A) Nonpolarized contact dermoscopes from Heine and Welch Allyn. (B) An assortment of polarized and hybrid dermoscopes from 3Gen.

(A: Courtesy of Heine, Herrsching, Germany, and Welch Allyn, Skaneateles Falls, NY; B: Courtesy of 3Gen, San Juan Capistrano, CA.)

Dermoscopic images seen with and without polarization can appear quite different, often providing complementary information. During naked-eye examinations of the skin, much of the light emitted toward the skin is reflected off of the stratum corneum due to the higher reflective index of the stratum corneum as compared to that of air. This precludes the observer from seeing structures below the stratum corneum. Nonpolarized dermoscopes require direct contact between the lesion and the glass plate of the dermoscope. In addition, the presence of a liquid interface (i.e., alcohol or oil) between the lesion and the glass plate is mandatory. The elimination of the air interface and the presence of the liquid reduces the amount of light reflected off the stratum corneum, thereby allowing the observer to see structures below the stratum corneum. The requirement of a liquid interface and direct skin contact can be eliminated with the use of polarized light and a cross-polarizing filter, as utilized in polarized dermoscopes. Although both NPD and PD allow the observer to visualize similar structures below the stratum corneum, subtle differences do exist. These differences tend to provide complementary information.

Nonpolarized dermoscopy works best for visualizing:

Polarized dermoscopy works best for visualizing:

Principles of Dermoscopy

The colors seen on dermoscopy, which are based on the depth of the melanin and other skin structures, are illustrated in Figure 32-2.

Figure 32-2 Colors seen on dermoscopy based on the depth of the melanin and other skin structures.

(Courtesy of Alfred W. Kopf, MD.)

Network Patterns

Pigment Network

A reticulated pigment network (Figure 32-3) has the following characteristics:

• The grid-like (honeycomb) network is composed of pigmented lines and hypopigmented “holes.”

• Network lines correspond to the rete ridge pattern of the epidermis.

• Network lines are visible due to melanin pigment in keratinocytes and melanocytes along the dermal/epidermal junction.

• The “holes” correspond to tips of the dermal papillae/suprapapillary plate.

Figure 32-3 Pigment network is created by melanocytes along the rete ridge seen from the skin surface producing a net-like (reticulated) pattern.

A typical pigment network in a benign nevus consists of (Figure 32-4):

• A relatively uniform line thickness and color

• A regularly meshed network

• Thinning (fading) at the periphery.

Figure 32-4 Typical pigment network (in a benign nevus). Note the regular line thickness and the fading of the lines at the periphery.

(Copyright Ashfaq A. Marghoob, MD.)

For an atypical pigment network (Figure 32-5),

• The lines of the network are not uniform in thickness and color.

• The lines are darker and/or broadened compared to a typical network.

• The “holes” are heterogeneous in size.

• The lines end abruptly at the periphery.

Figure 32-5 Atypical pigment network in a dysplastic nevus with variations in line thickness, darkness, and pattern.

(Copyright Richard P. Usatine, MD.)

A pseudonetwork (Figure 32-6) is

• Usually seen in pigmented lesions located on the face.

• Results when the rete ridge pattern is attenuated.

• Has adnexal openings (hair follicles and sweat glands) that form the holes of the pseudonetwork.

Figure 32-6 Pseudonetwork is the net-like pattern made by lightly-colored adnexal openings within pigmented lesions on the face. This is a solar lentigo with a typical moth-eaten border showing the adnexal openings within the pigmented lentigo.

(Copyright Ashfaq A. Marghoob, MD.)

A negative network is a reverse network that is seen in melanoma (Figures 32-7 and 32-8). It consists of dark, elongated, and curved globular structures surrounded by relative hypopigmentation. This results in the impression that the lines of the network appear lighter in color with an almost serpiginous pattern with holes that are darker in color (and appear sausage shaped).

Figure 32-7 Negative network (reverse network) in a microinvasive melanoma. The negative network consists of dark, elongated, and curved globular structures surrounded by relative hypopigmentation.

(Copyright Ashfaq A. Marghoob, MD.)

Figure 32-8 Negative network is created by large nests of melanocytes squeezing the rete ridges, making them into the lighter areas between the darker nests.

Other Structures

Chrysalis

• Seen only with polarized light dermoscopy.

• Consists of linear white lines/streaks that are oriented in an orthogonal fashion.

• The chrysalis structure (Figures 32-9 and 32-10) represents altered dermal collagen.

Figure 32-9 Melanoma with chrysalis (also known as crystalline structures) seen on the right side of the lesion. They consist of orthogonal white lines.

(Copyright Ashfaq A. Marghoob, MD.)

Figure 32-10 Chrysalis crystalline structures represent altered dermal collagen and can be seen in these four melanocytic and nonmelanocytic lesions: (A) melanoma; (B) Spitz nevus; (C) dermatofibroma; (D) basal cell carcinoma.

(Copyright Ashfaq A. Marghoob, MD.)

Structureless Areas

• Areas devoid of any discernible structures.

• The color is relatively hypopigmented compared to the surrounding nevus, but it is not white and it does not manifest any regression structures such as peppering.

• Results from a lack of pigment, attenuated rete ridges, or lack of contrast.

Dots

• Dots are small, round structures with a diameter of less than 0.1 mm.

• They are black, brown, blue-gray, or red in color.

• Black dots represent pigment in the stratum corneum.

• Brown dots represent small nevomelanocytic nests at the tips of the rete ridges, at the dermal/epidermal junction, or in the epidermis.

• Blue-gray dots represent free melanin in dermis or in macrophages.

• Red dots represent blood vessels.

 

Typical dots in benign melanocytic lesions are seen in Figure 32-11. Brown dots on the network appear in normal nevi (Figure 32-12). Brown dots off the network may appear in dysplastic nevi or melanoma (Figure 32-13).

Figure 32-11 Typical dots in benign melanocytic lesions are seen on the pigment network and are caused by a cluster of melanocytes at the base of the rete ridge.

Figure 32-12 Dermoscopy of benign nevus with typical dots on the network.

(Copyright Ashfaq A. Marghoob, MD.)

Figure 32-13 Invasive melanoma with atypical dots near the left edge and atypical globules in the upper left corner.

(Copyright Ashfaq A. Marghoob, MD.)

Globules

• Globules are symmetrical, round to oval structures that are larger than 0.1 mm (Figures 32-13 and 32-14).

• They are brown, black, blue, or red in color.

• Brown, black, and blue globules correspond to nests of pigmented melanocytes at the dermal/epidermal junction or in the dermis.

• Red globules represent blood vessels of neovascularization.

Figure 32-14 (A) Typical globules evenly distributed in a benign nevus. AM. (B) Atypical globules aggregated in the lower left corner of this dysplastic nevus.

(Copyright Ashfaq A. Marghoob, MD.)

Figure 32-14A shows typical globules evenly distributed in a benign nevus; Figure 32-14B shows atypical globules aggregated in the lower left corner of a dysplastic nevus.

Pseudopods

• Pseudopods are linear finger-like projections that radiate toward normal skin.

• They are located at the periphery of the lesion.

• They have small knobs at their tips that can make them look like tennis rackets.

 

Various types of pseudopods are shown in Figures 32-15 through 32-17.

Figure 32-15 Pseudopods. A, B, C, and F are true pseudopods; the others are not.

(Adapted from Menzies SW, Crotty K, McCarthy W. The morphologic criteria of the pseudopod in surface microscopy. Arch Dermatol. 1995;131:436–440.)

Figure 32-16 Pseudopods in a Spitz nevus that are nearly 360° around the nevus.

(Copyright Ashfaq A. Marghoob, MD.)

Figure 32-17 Pseudopods seen in a melanoma. These represent radial growth of the tumor.

(Copyright Ashfaq A. Marghoob, MD.)

Radial Streaming

The term radial streaming refers to radial, parallel, linear extensions that resemble pseudopods but do not have a knob at the ends (Figure 32-18). They are located at the periphery.

Figure 32-18 Radial streaming showing the radial growth pattern of nests of melanocytes in a melanoma or Spitz nevus.

Streaks

Streaks is a term that encompasses both pseudopods and radial streaming. These are seen in melanoma and Spitz nevi (Figures 32-15 through 32-19).

Figure 32-19 Streaks are visible with radial streaming on the right side of this invasive melanoma.

(Copyright Ashfaq A. Marghoob, MD.)

Blotch (Black Lamella)

• A blotch has a large concentration of melanin pigment.

• It extends throughout the epidermis and/or dermis.

• It visually obscures the underlying structures.

• A typical blotch in a benign nevus is often centrally located while an off-center blotch may be seen in a melanoma (Figure 32-20).

Figure 32-20 (A) Peripheral network with a central blotch in this benign nevus. (B) Atypical blotch (not centrally located) in a melanoma. Note the blue-white veil, atypical globules, atypical network, and the peripheral tan structureless areas.

(Copyright Ashfaq A. Marghoob, MD.)

Blue White Veil, Raised

• Area of focal irregular, indistinct, confluent, blue pigmentation (Figure 32-21).

• Focal overlying white ground-glass haze.

• Aggregation of heavily pigmented cells/melanin in the dermis (blue color) in combination with compact orthokeratosis (anuclear keratin layer).

Figure 32-21 Blue-white veil over raised area in a melanoma.

(Copyright Ashfaq A. Marghoob, MD.)

Figure 32-21 shows a blue-white veil over a raised area in a melanoma.

Blue White Veil, Flat

A flat blue-white veil is also called a white scar-like area with “peppering” or regression structures (Figure 32-22).

• Area of white scar-like depigmentation.

• Focal speckled multiple blue-gray granules (blue-white veil over flat area).

• Fibrosis, loss of pigmentation, epidermal thinning, effacement of the rete ridges, and melanin granules free in the dermis or in melanophages scattered in the papillary dermis.

Figure 32-22 Blue-white veil over flat area with “peppering.” These represent regression structures in a melanoma in situ.

(Copyright Richard P. Usatine, MD.)

Peppering

Also know as granularity, peppering is loose melanin in the dermis or melanin in melanophages.

Note that the blue-white veil (raised or flat) and peppering are melanoma-specific structures and should raise concern.

Structures in Nonmelanocytic Lesions

Seborrheic Keratoses

Milia-Like Cysts (Figure 32-23)

• Round whitish or yellowish structures.

• Commonly seen in seborrheic keratosis.

• They represent intraepidermal keratin-filled cysts.

 

Comedo-Like Openings (Figure 32-23)

• Commonly seen in seborrheic keratosis.

• They represent keratin-filled invaginations of the epidermis.

 

Gyri and Sulci (Figure 32-24)

• Have a cerebriform appearance.

• The gyri can sometimes resemble “fat fingers.”

Figure 32-23 Seborrheic keratosis with milia-like cysts and comedo-like openings.

(Copyright Ashfaq A. Marghoob, MD.)

Figure 32-24 Cerebriform seborrheic keratosis with gyri and sulci.

(Copyright Richard P. Usatine, MD.)

Basal Cell Carcinoma (BCC)

Leaf-Like Areas (Figures 32-25 and 32-26)

• Brown to gray-blue discrete bulbous blobs.

• “Leaf-like” pattern.

 

Blue-Gray Ovoid Nests (Figure 32-27)

• Large and well circumscribed.

• Confluent pigmented ovoid areas.

 

Spoke-Wheel-Like Structures (Figure 32-27)

• Well circumscribed.

• Brown to gray-blue-brown.

• Radial projections.

• Meeting at a darker brown central hub.

Figure 32-25 Leaf-like structures in a pigmented BCC.

(Copyright Richard P. Usatine, MD.)

Figure 32-26 Leaf-like structures and blue-gray ovoid nest in bottom left-hand corner of this BCC.

(Copyright Richard P. Usatine, MD.)

Figure 32-27 Spoke-wheel-like structures and isolated blue-gray ovoid nest on the left.

(Copyright Ashfaq A. Marghoob, MD.)

Arborizing blood vessels are seen in BCC (Figure 32-28).

Figure 32-28 Arborizing blood vessels like branching trees in a BCC.

(Copyright Richard P. Usatine, MD.)

Angioma/Angiokeratoma

Angiomas have red lacunae (lagoons) (Figure 32-29). Angiokeratomas have red, maroon, blue, and black lacunae (lagoons) (Figure 32-30). Their vascular architecture is described in Figure 32-31.

Figure 32-29 Hemangioma showing red lacunae (lakes or lagoons of sharply demarcated vascular tissue).

(Copyright Richard P. Usatine, MD.)

Figure 32-30 Angiokeratoma showing purple and black lacunae.

(Copyright Ashfaq A. Marghoob, MD.)

Figure 32-31 Vascular architecture seen by dermoscopy.

(Adapted from Malvehy J, Braun RP, Puig S, et al. Handbook of Dermoscopy. London: Informa Healthcare; 2006:30–31, Table 4-4.)

Two-Step Dermoscopy Algorithm

The two-step dermoscopy algorithm forms the foundation for the dermoscopic evaluation and differentiation of skin lesions (Figure 32-32). If a lesion manifests any of the structures listed below, it is considered to be a melanocytic lesion:

Figure 32-32 Two-step algorithm.

Figure 32-33 Atypical network in a junctional dysplastic nevus.

(Copyright Richard P. Usatine, MD.)

Figure 32-34 Nevus on the sole of the foot showing parallel network pigment in the furrows rather than the ridges. Note the white eccrine gland openings on the ridges, which are wider than the furrows.

(Copyright Richard P. Usatine, MD.)

Figure 32-35 Pseudonetwork pattern is seen on the face in this congenital nevus.

(Copyright Richard P. Usatine, MD.)

Figure 32-36 (A) Network, (B) aggregated globules, (C) streaks, and (D) homogeneous blue nevus are four patterns seen in melanocytic lesions.

(Copyright Ashfaq A. Marghoob, MD.)

Note, however, an exception: a pattern consisting of a delicate network surrounding a scar-like area is associated with dermatofibroma. This particular pattern trumps the presence of a network structure; thus, despite the presence of a network, this type of lesion is not considered to be melanocytic (Figures 32-37 and 32-38).

Figure 32-37 Pattern trumps network in this dermatofibroma. Although this appears to have a peripheral network, the central stellate scar makes this a dermatofibroma, which is not a melanocytic lesion.

(Copyright Richard P. Usatine, MD.)

Figure 32-38 The first step of the two-step diagnostic algorithm requires all lesions to be separated into melanocytic (A) or nonmelanocytic (B). If the lesion is determined to be non-melanocytic (B) then it must manifest criteria diagnostic of basal cell carcinoma, dermatofibroma, seborrheic keratosis or hemangioma. If the lesion is determined to be melanocytic (A) then one needs to proceed to the second step of the two-step algorithm. The second step requires the observer to differentiate nevi from melanoma.

If the lesion does not manifest any of the structures mentioned above, look for features of:

BCC has at least one of these:

Seborrheic keratoses exhibits these characteristics (Figure 32-39):

Figure 32-39 A seborrheic keratosis can have all or any of these structures.

(A, D: Adapted from Malvehy J, Braun RP, Puig S, et al. Handbook of Dermoscopy. London: Informa Healthcare; 2006:83, Figure A-21.)

Figure 32-40 SK with hairpin vessels surrounded by a whitish halo.

(Copyright Richard P. Usatine, MD.)

Vascular lesions have red or blue-black lacunae (see Figures 32-29 and 32-30).

If the lesion has no melanocytic features and it has no features seen in one of the four common nonmelanocytic lesions, then search for any vascular structures/patterns as seen in Figures 32-31 and 32-41. If the lesion has no features of a melanocytic lesion, DF, BCC, SK, or hemangioma and it also lacks diagnostic vascular structures, then the lesion is considered structureless. All structureless lesions are by default considered to be melanocytic and one needs to consider the diagnosis of melanoma. These lesions should be biopsied or monitored very closely. Figure 32-42 puts this all together in one algorithm.

Figure 32-41 Benign vascular patterns.

Figure 32-42 Putting it all together.

Pattern Analysis

Practitioners should look for the “ugly duckling” or the “Beauty and the Beast” sign. The ugly duckling is the lesion that stands out as different compared to surrounding nevi. Another way of looking at this is that the ugly lesion is the “Beast” and the other benign lesions are the “Beauty.”⁷

Figure 32-43 Benign nevi tend to adhere to 1 of 10 recurrent patterns. Melanoma is a melanocytic lesion that deviates from the 10 benign patterns.

(Adapted from Malvehy J, Braun RP, Puig S, et al. Handbook of Dermoscopy. London: Informa Healthcare; 2006:91, Figure A-36.)

Melanoma deviates from global benign patterns and has at least one of these local features (Figure 32-44):

Figure 32-44 Melanoma-specific structures.

(Adapted from Malvehy J, Braun RP, Puig S, et al. Handbook of Dermoscopy. London: Informa Healthcare; 2006:75, Figure A-4.)

The sensitivity and specificity of melanoma structures and features are shown in Table 32-1. A three-point checklist can be applied to pigmented lesions only:

Final score and recommended treatment:

Special Conditions

Face

Rete ridges on the face are not prominent, especially in elderly people. Adnexal structures, hair follicles, and sweat glands are more prominent on the face and produce the pseudonetwork. Lentigo maligna is an important early melanoma that should be recognized on the face before it becomes invasive.

Three important dermoscopic features are:

1. Asymmetric pigmented follicular openings

2. Dark rhomboidal structures

3. Slate-gray dots.¹²

 

Schiffner et al. described the progression model for lentigo maligna that is detailed in Figure 32-45.¹² Figure 32-46 shows actual lentigo maligna with rhomboidal structures.

Figure 32-45 Lentigo maligna in the various stages of the progression model.

Figure 32-46 Lentigo maligna on the face with rhomboidal structures.

(Copyright Ashfaq A. Marghoob, MD.)

Acral Areas—Palms and Soles

To understand how to differentiate melanoma from other pigmented lesions on the palms or soles, the practitioner must understand the anatomy of the acral skin. The dermatoglyphics on acral skin consists of mountains and valleys (ridges and furrows) with eccrine sweat glands that are found on the mountains (Figure 32-47). The mountains are wider than the valleys.

Figure 32-47 Acral skin consists of mountains and valleys (ridges and furrows) with eccrine sweat glands that are found on the mountains. The mountains are wider than the valleys.

Benign nevi have three common patterns:

1. Parallel furrow (pigment running along the valleys)

2. Lattice-like (pigment that creates a lattice)

3. Fibrillar (thin parallel lines that cross over the mountains and valleys).

 

Melanomas also have three common patterns:

1. Parallel ridge (pigment running along the mountains)

2. Diffuse pigmentation (pigment in large blotches of different shades)

3. Irregular dots and globules.

 

Figure 32-48 shows the pigment of a benign nevus in the furrows or valleys. There is also a lattice-like pattern and the pigment is seen running in the furrows with a cross network between the furrows.

Figure 32-48 Pigment of a benign nevus on the sole of the foot in the furrows (valleys).

(Copyright Richard P. Usatine, MD.)

Ninety-eight percent of melanomas on the palms and soles have a parallel ridge pattern in which the pigment is on the mountains and there is hypopigmentation of the valleys. Zero percent of acral nevi have this pattern. Figure 32-49 shows an acrolentiginous melanoma on the foot with this parallel ridge pattern. Sometimes the eccrine sweat gland openings are visible in the middle of the ridges of hyperpigmentation.

Figure 32-49 Acrolentiginous melanoma on the foot with a parallel ridge pattern.

(Copyright Ashfaq A. Marghoob, MD.)

It is important not to confuse hemorrhagic lesions on the palms or soles with melanoma to avoid unnecessary biopsies. Frequently the history alone will help to distinguish pigmentation caused by trauma or ill-fitting shoes from a benign or malignant pigmented lesion. These subcorneal hemorrhages can appear yellow-red to red-black in color and may have globules at the periphery or look like pebbles on the ridges. The heel and bottom of the big toe are common locations for subcorneal hemorrhages seen with sports or ill-fitting shoes. Figure 32-50 is an example of a benign subcorneal hemorrhage.

Figure 32-50 Benign subcorneal hemorrhage can resemble a melanoma. The subcorneal blood is sequestered on the ridges creating a pattern that mimics melanoma.

(Copyright Ashfaq A. Marghoob, MD.)

Scabies

The dermatoscope can also be used for the diagnosis of scabies. Look for burrows in the skin and put the dermoscope over the burrow. Figure 32-51 shows scabies mites at the ends of the burrows. The mites are visible and resemble an arrowhead pointing away from the burrow (Figure 32-51). That is because the mite is in the process of burrowing through the skin using its mouth and legs to extend the tunnel. The round shape of the mite is also visible. This finding should be sufficient to confirm a suspected case of scabies. Once the mite has been identified with a dermoscope, a directed scraping may be used to see the mite, its eggs, or its feces under the microscope.

Figure 32-51 Two scabies mites at the end of two distinct burrows. The head and anterior legs are most visible and resemble arrowheads pointing away from the burrows.

(Copyright Richard P. Usatine, MD.)

Conclusion

Dermoscopy is not learned overnight and this chapter is a good introduction to begin learning this important tool for diagnosis. Use the list of resources below to continue your learning.

Resources