III.9.1 Definition
The definition involves benign melanocytic nevi, localized on the genitalia or other particu- lar body sites, which often display atypical clini- cal and/or histopathological features that may mimic melanoma.
III.9.2 Clinical Features
Pigmented genital lesions, including melano- cytic nevi, melanotic macules, and melanoma, are observed in about 10% of men and women.
Melanocytic Nevi on the Genitalia and Melanocytic Nevi
on Other Special Locations
Ingrid H. Wolf
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Contents
III.9.1 Definition . . . .119
III.9.2 Clinical Features . . . .119
III.9.3 Dermoscopic Criteria . . . .120
III.9.4 Relevant Clinical Differential Diagnosis . . . .120
III.9.5 Histopathology . . . .120
III.9.6 Management . . . .121
III.9.7 Case Study . . . .122
References . . . .123
Vulvar nevi occur in about 2% of women. Geni- tal melanocytic nevi are more likely noted in younger patients, especially in premenopausal women. The main locations are the vulva in- cluding labia minora/majora, the clitoris, and the glans penis. They present as asymmetrical pigmented macules or papules, uniform or var- iegated in color, usually with a diameter of less than 1 cm (Fig. III.9.1a).
Melanocytic proliferations in concurrence with lichen sclerosus et atrophicus involving genital skin are significant. This association is uncommon but may be a challenging diagnostic problem because the changes can lead to an er- roneous diagnosis of persistent/recurrent mela- nocytic nevus or melanoma [5].
Closely related to melanocytic nevi on the genitalia – with similar clinical and histopatho- logical features – are benign atypical melano- cytic proliferations which are located on the skin of particular body sites including the milkline, flexural locations [7], and other ana- tomical areas (Fig. III.9.2; Table III.9.1) [8].
Milkline nevi are found on the lines (mammary
streaks) extending from the axilla through the
areola- and periumbilical region to the groin
and genitalia, bilaterally. Awareness of all these
lesions, which belong to the spectrum of pseu-
domelanomas, is of practical importance, as
they may pose problems in differentiating them
from melanoma.
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III.9.3 Dermoscopic Criteria
Melanocytic nevi on the genitalia and on other special sites frequently reveal a regular pigment network (Fig. III.9.1b). Sometimes, however, an atypical brown to black network, and some ir- regular streaks or blotches at the periphery, are observed [6, 9]. A special honeycomb-like pig- mentation may be observed in melanocytic nevi of the areolar region.
III.9.4 Relevant Clinical Differential Diagnosis
Many genital melanocytic nevi are “common”
lesions with no real differential diagnosis. In the cases where distinctive atypical findings are present, these melanocytic proliferations can simulate melanoma, Spitz’s nevi, and non-ne- void melanotic macules.
III.9.5 Histopathology
Unusual histopathological features are found only in the epidermis, whereas the dermal changes are typical for a benign acquired or congenital melanocytic compound nevus with signs of maturation.
Within the epidermis, nests of melanocytes, which can vary markedly in sizes and shapes
Fig. III.9.1. Melanocytic nevus on the glans penis.
a Asymmetrical, poorly circumscribed, mottled lesion in shades of brown and white. b Dermoscopy reveals a pig- ment network, whitish structures, globules, and parallel lines. c Histopathology: nests of different sizes and shapes with a “dyscohesive” pattern confined to the dermo-epi- dermal junction. Note dermal melanocytes and fibrosis
Table III.9.1. Site-specific melanocytic nevi Location
Genitalia, scrotum Breast, mammilla, nipple
Axilla, inguinal region, perineal/perianal area Popliteal/antecubital fossa
Umbilicus Palms and soles Knee
Ear
Scalp
Conjunctiva
and tend to confluence, are found mainly along the dermo-epidermal junction. Clefts around the nests (dyscohesive pattern) are a character- istic finding (Fig. III.9.1c). There may be a pre- dominance of solitary melanocytes that exhibit focal upward pagetoid spread. Individual mela- nocytes can sometimes feature large nuclei with abundant pale cytoplasm [1–4].
III.9.6 Management
The tumors are commonly excised with a small surgical margin, particularly when the clinical and dermoscopic features are suggestive for ma- lignancy. Aggressive surgical treatment in areas in which conservation of tissue is especially im- portant should be avoided.
Fig. III.9.2. The many faces
of melanocytic nevi on the
vulva (a, b), umbilicus (c),
and axilla (d)
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III.9.7 Case Study
Patient Comment
An 8-year-old girl presented with a 3¥2-cm long-standing lesion on the left breast, present since birth.
Question Asked By the Physician
Has growth of the lesion been observed recent- ly?
Differential Diagnosis
The differential diagnosis was melanoma, ne- vus, keratosis areola mammae, naeviformis.
The diagnosis was atypical melanocytic nevus of the mamilla, “milk-line” nevus.
Management
The management was digital follow-up and sur- gical excision.
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