Dermal Nevi

Dermal nevi are commonly occurring, benign melanocytic tumors that mostly develop in adulthood. They can be categorized into 2 main subtypes, which differ clinically and dermoscopically: Miescher nevi (on the face) and Unna nevi (located particularly on the trunk, extremities, and neck). Clinically, both Miescher and Unna nevi are usually long-standing lesions without a history of recent change. Miescher nevi, however, are smooth and dome-shaped, with a semifirm consistency (which may at times mimic nodular basal cell carcinoma [nBCC]). Conversely, Unna nevi are soft and papillomatous.

Both types of dermal nevi are characterized dermoscopically by coarse comma-shaped vessels, which are pinkish in color and slightly blurred. Comma vessels have a positive predictive value (PPV) for dermal nevi of 94% and are a significant negative predictor for amelanotic/hypomelanotic melanoma (AHM). The vessels of Miescher nevi are basically comma-shaped but can be somewhat variable in morphology (ie, varying in size and shape and frequently elongated) ( Fig. 1 A ). These vessels differ from the sharply focused, bright red arborizing telangiectasias of nBCC, which at times may be mistaken clinically for dermal nevus on the face. Like Miescher nevi, the comma vessels of Unna nevi are pinkish and slightly unfocused, but they differ in having a more classically comma shape, with less variation in size or shape (see Fig. 1 B).

( A ) Clinical ( inset ) and dermoscopic views of a long-standing dermal (Miescher) nevus on the upper cutaneous lip of a 61-year-old woman. Clinically, the lesion had a diameter of 4 mm, was semifirm, smooth, and dome-shaped. On polarized contact dermoscopy, slightly blurred, pinkish comma-shaped vessels can be discerned ( arrows ), along with remnants of a tan pseudonetwork. Although Miescher nevi on the face may clinically mimic nBCC, dermoscopy usually facilitates a ready differentiation between the sharply focused, bright red arborizing vessels of BCC and the slightly blurred, pinkish comma vessels of dermal nevi. ( B ) Clinical ( inset ) and dermoscopic images of a long-standing dermal (Unna) nevus, located on the abdomen of a 42-year-old woman. Clinically, the lesion was soft and papillomatous. Nonpolarized contact dermoscopy exhibits exophytic papillary structures, keratin-filled crypts ( arrows ), and a fairly regular arrangement of comma vessels. A fairly homogeneous, tan-colored background was also apparent. The patient requested removal of the lesion due to it catching on clothing. Histopathologic examination revealed a dermal nevus.

Additional dermoscopic features of Miescher nevi include structureless tan-brown remnants of pigmentation and/or remnants of a pigmented pseudonetwork. Conversely, Unna nevi often display exophytic papillary structures, keratin-filled crypts, residual brown globules, and hairs.

Nonpigmented (Red) Clark Nevi

Nonpigmented or red Clark (atypical) nevi usually present as pink to pinkish-tan lesions of diameter greater than 5 mm in fair-skinned white patients (ie, skin phototype I or II). Red nevi are often multiple but may present as solitary lesions (ie, with or without the presence of other, pigmented nevi). Red nevi may present as macules, papules, or maculopapular tumors and can be difficult at times to distinguish clinically from AHM, particularly when presenting as ugly duckling lesions. Such ugly duckling lesions include solitary or relatively large red nevi.

On dermoscopy, red Clark nevi typically show dotted and comma vessels, arranged fairly regularly throughout the lesions and occurring on a pinkish-tan background ( Fig. 2 ). The tan background may have a reticular or homogeneous appearance. These features generally contrast with nonpigmented Spitz nevi, which are usually solitary and fast growing and typically display a more dense arrangement of dot vessels on a pink-to-red background. In addition, reticular depigmentation, whitish striae, and remnants of pigmentation (eg, black dots, brown globules, and blue color) may additionally be seen in Spitz nevi. Dermoscopic examination of red nevi is also helpful in differentiating these tumors from AHM. Like Spitz nevi, AHM can present as solitary, fast-growing lesions and can exhibit a fairly dense arrangement of dot vessels on a pink-to-red background. In AHM, reticular depigmentation, whitish striae, remnants of pigmentation (eg, black dots, brown globules, blue color, and other melanoma-specific features), atypical vessels (eg, hairpin and linear irregular vessels) and ulceration may be additional clues for the diagnosis.

Red Clark nevus. Clinical view of an 8 × 6 mm soft, smooth, pinkish plaque on the back of a 43-year-old Australian man with skin phototype I/II and a history of BCC ( inset ). The tumor was one of many similar pink lesions on the trunk. Polarized noncontact dermoscopy reveals dotted and comma vessels in a fairly regular arrangement, occurring on a pinkish-tan background.

In patients presenting with multiple red Clark nevi, dermoscopic comparison of all the lesions should be performed to ensure comparable dermoscopic features of these nevi. To avoid missing a possible AHM, dermoscopic ugly duckling red Clark nevi–like tumors (ie, dermoscopically unlike the other red nevi on a given patient), solitary red tumors, lesions with a history of recent change, or lesions showing melanoma specific criteria should be excised.

Spitz Nevi

Spitz lesions were originally described in 1948 as juvenile melanomas by the pathologist, Sophie Spitz. Spitz believed that these lesions were childhood melanomas with a largely innocuous course (ie, rarely metastasizing, unlike adult melanomas). Of Spitz’ original 13 cases, at least 1 proved to be an actual malignancy (as evidenced by metastases and death), with the remainder having a benign biologic course.

Spitz lesions nowadays are generally considered benign entities (ie, nevi) that can mimic malignant melanoma both clinically and histopathologically. Recently, however, some investigators have challenged this mainstream view and echoed Spitz’ original conclusions, hypothesizing that Spitz tumors may actually be a low-grade cutaneous malignancy with a high tendency to self-limitation and involution.

Spitz nevi classically present as fast-growing, smooth, dome-shaped papules or nodules. They are frequently pink or reddish in color but also commonly pigmented. They occur more commonly in children, especially on facial sites. As discussed previously, Spitz nevi assume significance because they are at times difficult to distinguish from melanoma on clinical grounds. In this setting, dermoscopy can be of assistance to clarify the diagnosis or at least raise a red flag for excision.

In flat nonpigmented Spitz nevi, dermoscopy stereotypically reveals dotted vessels that appear fairly closely aligned in a regular arrangement. The vessels lack whitish haloes and typically occur on a pink to red (milky red) background ( Fig. 3 A ). Dot vessels lacking white haloes are highly predictive for melanocytic skin tumors (PPV of 90%) and are particularly prevalent in Spitz nevi. Other dermoscopic features of flat Spitz nevi include reticular depigmentation (or negative network), a white network-like structure formed by intersecting white lines that surround the abovementioned dot vessels. White striae (chrysalis structures) can also be seen in some lesions and consist of shiny white orthogonal lines visible under polarized light dermoscopy. In Spitz nevi having pigment remnants, black dots, brown globules, bluish areas, and regions of pigmented network or streaks (ie, a residual starburst pattern) may also be apparent.

( A ) Clinical ( inset ) and dermoscopic images of a 4 × 3 mm pinkish plaque, located on the dorsum of the foot of a 21-year-old woman. Polarized contact dermoscopy reveals whitish reticular depigmentation (negative network), dotted and coiled vessels. The vessels lack white haloes and are fairly closely and regularly arranged. Tan pigmentation is seen peripherally. Histopathologic examination confirmed the diagnosis of Spitz nevus. ( B ) Clinical ( inset ) and dermoscopic photographs of a 1-cm pinkish, verrucous nodule, located on the knee of a 4-year-old boy. Polarized contact dermoscopy demonstrates whitish surface scale, exophytic papillary structures, and a polymorphous vascular pattern. The latter comprises a combination of dotted, coiled, hairpin, linear irregular, and a few branching vessels. The vessels lack whitish haloes and occur on a pinkish-white background. Numerous milky pink globules ( rectangle ) and a few brown dots and globules ( ovals ) are also present. Histopathologic examination confirmed the diagnosis of Spitz nevus.

Nonpigmented atypical and nodular Spitz tumors typically display a polymorphous vascular pattern, with linear irregular vessels, coiled vessels, and/or milky red or pink globules. If partially pigmented, pigment remnants, such as homogeneous bluish areas and brown globules, may be visualized (see Fig. 3 B).

Because AHM, Spitz nevi, and atypical Spitz tumors can show similar dermoscopic features, excision should be performed for all nonpigmented spitzoid-looking lesions in adult patients. In children (ie, up to the age of 12 years), a more conservative approach is currently used when dealing with nonpigmented Spitz lesions exhibiting a stereotypical appearance. Contrarily, excision should be performed for large (>1 cm), nodular, rapidly changing, ulcerated, or otherwise atypical Spitz tumors appearing in childhood.

Sebaceous Hyperplasia

SH is a benign, nonpigmented neoplasm frequently presenting as multiple papules on the forehead, nose, and cheeks of middle-aged to elderly patients. Lesions are smooth, have a yellowish hue, and may have a central dell visible to the naked eye. Although a diagnosis is reliably made in many instances on clinical grounds alone, SH may at times be difficult to distinguish from other conditions, such as basal cell carcinoma (BCC).

Dermoscopy aids in the correct identification of SH by revealing crown (wreathlike) vessels, seen as pinkish, elongated, slightly blurred, and scarcely branching telangiectasias that surround the tumor (ie, in a radial arrangement). These vessels do not usually cross over the central parts of the lesion. The latter is in contrast to the arborizing telangiectasias of nBCC, which are typically bright red in color, sharply focused, and often pass over the center of the lesion. Multiple white to yellow, aggregated, homogeneous globular areas are also characteristically seen, which correspond histopathologically to the enlarged sebaceous lobules of SH. Moreover, a small centrally located yellowish crater (or craters) may be present on dermoscopy, which correlates with the dilated ostium (or ostia) of the infundibulum of the sebaceous glands ( Fig. 4 A ).

( A ) Clinical ( inset ) and dermoscopic views of a long-standing, 3-mm, whitish-pink papule located on the forehead of a 79-year-old man with skin phototype II. Polarized contact dermoscopy highlights the aggregated whitish globular structures, yellowish ostia (ie, openings of the infundibula) ( arrows ), and crown vessels at the periphery. The latter are scarcely branching and pass toward the center of the lesion but do not cross over it. The crown vessels of SH contrast with arborizing vessels of nBCC, which are bright red, sharply focused, and often course over the central parts of the tumor. ( B ) Clinical ( inset ) and dermoscopic views of a 4–5 mm, slightly raised, lightly pigmented plaque, located on the back of a 77-year-old woman (with skin phototype I/II). Nonpolarized contact dermoscopy supports the diagnosis of SK by revealing multiple large whitish milia cysts and a fairly regular arrangement of fine hairpin vessels.

Seborrheic Keratosis

SKs are common benign acanthomas that commonly present as rough, well-demarcated, skin-colored to brown to black papules and plaques in adult patients. They are particularly prevalent on the trunk, face, and extremities and stereotypically have a stuck-on appearance. When nonpigmented, SK may clinically resemble other lesions, such as verruca, squamous cell carcinoma (SCC), or even AHM.

Dermoscopy assists in improving the accuracy of diagnosis of nonpigmented SK by revealing hairpin vessels (capillary loops) of fairly monomorphous morphology, arranged in a regular pattern. Hairpin vessels may occur in several different types of skin tumors but, when surrounded by white haloes, are suggestive of keratinizing lesions. Furthermore, hairpin vessels are particularly characteristic of SK, having a PPV for SK of 70%, compared with only approximately 13% for (invasive) SCC. In further contrast to SK, hairpin vessels in invasive SCC are usually elongated and irregular in morphology and occur in an irregular distribution.

Additional dermoscopic features of SK include a well-demarcated edge, a brainlike appearance with gyri and sulci (ridges and fissures), multiple whitish milia cysts, and pseudocomedone openings (crypts) (see Fig. 4 B).

Irritated or traumatized SK may at times pose a diagnostic and management dilemma, because they can clinically simulate malignant conditions, such as melanoma or SCC. This is especially the case if a history of recent trauma is not recalled by a patient. On dermoscopy, the hairpin vessels may be enlarged or elongated and appear somewhat irregular in morphology. Signs of recent trauma, namely blood crusts and/or erythema (inflammation), are also typically seen. Such features can make a dermoscopic diagnosis challenging. Remnant areas showing specific features of SK (ie, well-demarcated edge, multiple large milia cysts, crypts, fissures and ridges), however, may be present, which suggest the correct diagnosis of traumatized SK. Close clinical follow-up typically reveals that the features of trauma subside within a few weeks. In doubtful cases, however, where a diagnosis of malignancy cannot be ruled out, biopsy at the outset is recommended.

Benign pink lichenoid keratosis (LK) is considered a variant of SK and presents as a scaly or smooth, pinkish macule, plaque, or papule that may be pruritic. The lesion is especially prevalent on the trunk and extremities of middle-aged to elderly patients and can clinically mimic several lesions, such as psoriasis, AK, SCCIS, BCC, and even amelanotic melanoma (AM). Dermoscopically, surface scale may be highlighted and dotted or coiled and/or telangiectatic vessels may be seen, the vessels typically arranged in a fairly regular pattern ( Fig. 5 ). In lesions with pigment remnants, tan-gray blotches may be present. Because the dermoscopic features of pink LK can overlap with nonpigmented malignant tumors, however, such as early SCCIS, BCC, or AHM, biopsy is recommended.

Clinical ( inset ) and dermoscopic images of a scaly, reddish macule located on the thigh of a 63-year-old woman, who had a history of psoriasis. The lesion had been pruritic. On polarized noncontact dermoscopy, diffuse whitish scale is seen in conjunction with a fairly regular array of dotted and coiled vessels. The dermoscopic differential diagnoses included psoriasis, pink LK, and early SCCIS. Histopathologic examination confirmed the diagnosis of benign LK.

Clear Cell Acanthoma (and Large Cell Acanthoma)

CCA, also called Degos or pale cell acanthoma, is an uncommon benign epithelial tumor that usually presents clinically as a solitary, pink to red plaque, papule, or nodule in middle-aged or elderly patients. Additionally, a scaly surface is sometimes present and a scaly collarette may be visible around the edge of the lesion. Many other benign and malignant nonpigmented skin lesions may resemble CCA clinically, including SK, BCC, SCC, and AM.

Dermoscopy assists in the identification of CCA by showing a striking pattern of dot and/or coiled vessels arranged in a linear, stringlike distribution ( Fig. 6 A ). At times, these linear patterns may assume a reticular arrangement. In addition, a whitish scaly surface may be highlighted by dry dermoscopy (ie, without immersion fluid) as well as a translucent to whitish peripheral scaly collarette. In contrast to the dot vessels seen in melanocytic lesions (including melanoma), the vessels in CCA are surrounded by whitish haloes or occur on a whitish background, as is customary for keratinizing tumors. Furthermore, the stringlike pattern of CCA contrasts with the typically regular arrangement of dot vessels in melanocytic skin lesions. In thicker variants of CCA, the vessels may appear coiled (or even glomerular), but they essentially retain their typical stringlike arrangement.

( A ) Clinical ( inset ) and dermoscopic images of a 2–3 mm smooth, solitary pink papule, located on the chest of a 57-year-old Australian man. Nonpolarized contact dermoscopy revealed a string of pearls vascular pattern (ie, dotted and coiled vessels arranged in a linear fashion) on a whitish background. Histopathologic examination confirmed the diagnosis of CCA. ( B ) Clinical ( inset ) and dermoscopic photographs of a 4-mm pink papule situated on the right lower back of a 61-year-old man. Polarized contact dermoscopy disclosed dotted and coiled vessels in linear arrays, reminiscent of CCA. The lesion was biopsied and histopathologic examination revealed a LCA. (Note: an incidental focus of acute suppurative folliculitis is present at the right side of the dermoscopic image.)

LCA is another rare, benign acanthoma that can at times present as a (scaly) pink papule or plaque on the trunk or extremities of middle-aged to elderly patients. Differential diagnoses may include SK, SCCIS (Bowen disease), BCC, and AM. Although considered highly specific for CCA, it is the experience of the authors that a stringlike (or reticular) arrangement of dotted and coiled vessels may also be seen in LCA (see Fig. 6 B). Further studies on the dermoscopic features of LCA, however, are needed.

Acantholytic Dyskeratotic Acanthoma (Acantholytic Dyskeratoma)

Acantholytic dyskeratotic acanthoma (acantholytic dyskeratoma) is a benign lesion typically presenting as a smooth to scaly-topped papular, pinkish tumor on the trunk of middle-aged to elderly patients. The lesion usually presents as a solitary tumor less than 1 cm in diameter and clinical differential diagnoses may include SK, verruca, nevus, BCC, AK, SCCIS, and invasive SCC.

On dermoscopy, acantholytic dyskeratoma may reveal tan to darker brown–colored, starlike (stellate) shapes consisting of surface scale and/or superficial indentations (microfissures). These features are hardly visible with the unaided eye. Tan-brown areas can appear in some lesions as broken-up and branching lines and/or discrete rounded areas. Similar brown stellate shapes can be seen in papules of transient acantholytic dermatosis (Grover disease), another condition displaying acantholytic dyskeratosis on histopathology.

In addition, the tan-brown superficial scaly starlike areas typically have whitish edges and occur on a white to pink to tan background ( Fig. 7 ). Very faint and fine dotted hairpin and linear vessels may also be visible, having a regular morphology and whitish haloes, the latter feature typically seen in keratinizing tumors. The tan-brownish keratotic areas of acantholytic dyskeratoma may at times be relatively large and round or oval in shape, reminiscent dermoscopically of the central yellowish-brown keratotic plugs or (giant) pseudocomedones seen in Darier disease.

( A ) Clinical photograph of a solitary 4–5 mm pink papule on the back of a 73-year-old Australian man with chronically sun-damaged skin (skin phototype I/II). ( B ) On noncontact polarized light dermoscopy, tan-colored starlike shapes and rounded areas are seen. The tan-colored areas appear scaly, have whitish edges, and occur on a pinkish-tan background. Histopathologic examination revealed features of acantholytic dyskeratosis. The clinical, dermoscopic and histopathologic findings were consistent with the diagnosis of acantholytic dyskeratotic acanthoma.

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