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Context.-Atypical genital nevus is rare and the only poorly documented melanocytic lesion in the spectrum of nevi of special sites. It is characterized by unique and reproducible histologic features, which may appear alarming and may raise significant concern for a diagnosis of melanoma.
Objectives.-To present the clinical and histologic features of atypical genital nevus with emphasis on distinction from vulvar melanoma.
Data Sources.-The findings are based on a review of the current literature.
Conclusions.-Atypical genital nevus is most often found in the vulva of premenopausal women. Despite the alarming histologic features, its clinical behavior appears benign with only rare local recurrence after incomplete removal. Recognition of this unusual melanocytic lesion and its characteristic histologic features is important to avoid overdiagnosis of invasive melanoma, with subsequent wide excision or sentinel lymph node biopsy, especially in view of the sensitive anatomic location.
(Arch Pathol Lab Med. 2011;135:317-320)
Vulvar melanocytic nevi are rare and represent only 2.3% of clinically pigmented vulvar lesions.1,2 Most vulvar nevi are compound or intradermal nevi, but other variants, such as congenital, dysplastic, blue, and Spitz nevi, have rarely been reported.3-6 An uncommon but distinctive melanocytic lesion presenting in the genital area of premenopausal women was first reported by Friedman and Ackerman7 in 1981. To reflect the often worrying histologic features, which can suggest a possible diagnosis of melanoma, the term atypical melanocytic nevus of genital type was subsequently proposed by Clark et al8 in 1998. This is frequently abbreviated to atypical genital nevus (AGN). The histologic features are unique to the genital area,3 and AGN may be regarded as a melanocytic nevus with site-specific features and atypia similar to atypical acral nevi, flexural nevi, nevi from the breast, or conjunctival nevi.9-12 The precise incidence of AGN is unclear, but it represents approximately 10% of all pigmented lesions and 5% of melanocytic nevi in the genital area.3,13
CLINICAL PRESENTATION
Atypical genital nevus characteristically presents on the lower genital tract of premenopausal women.3,7-10,13,14 Presentation in childhood is common, and more than 50% of patients are younger than 20 years.14 The vulva, including labia majora, labia minora, and clitoris, is most frequently affected, followed by the mons pubis and perineum.3,7,8,14,15 There is an equal distribution on mucosal surfaces and hair-bearing skin, but a strong predilection...