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A 20-year-old woman is requesting evaluation of a mole on the sole of her left foot. The lesion had been present for several years and remained unchanged. She sought consultation after reading a newspaper article on melanoma. The patient’s personal and family history are negative for skin cancer. She has experienced frequent sunburns as a child as well as the occasional use of indoor tanning beds. Examination reveals an irregularly shaped hyperpigmented macule. Scattered nevi were noted elsewhere on her body.
Acral melanocytic nevi (AMN) are benign pigmented lesions commonly found on the volar surfaces of the palms and soles, as well as within the nail unit. Their prevalence in the US population ranges from 23% to 42%, with higher rates...
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Acral melanocytic nevi (AMN) are benign pigmented lesions commonly found on the volar surfaces of the palms and soles, as well as within the nail unit. Their prevalence in the US population ranges from 23% to 42%, with higher rates observed in Asian populations.1
Less lesions are more commonly seen in females, in individuals under the age of 50, and more with darker skin pigmentation.2 Most are typically smaller than 0.6 cm and present as macules with light brown to black coloration. The etiology of some AMN may be linked to mutations of the BRAF and NRAS (part of the RAS family) genes.1
Dermoscopy plays a valuable role in recognizing AMN, revealing a classic linear pigmentation along the sulci of the skin markings (parallel furrow pattern).3 In contrast, acral melanomas typically exhibit a parallel ridge pattern that may be accompanied by irregular streaks, globules, and blue-white veils. Other benign dermoscopic patterns include lattice-like and fibrillar patterns.3
Histologic differentiation of AMN from early acral melanoma can be challenging. Benign AMN features are characterized by small, symmetric, and well-circumscribed lentiginous and nested melanocytic proliferation, while the latter favors extensive pagetoid scatter, severe cytologic atypia, and dermal mitoses.1,4
Stephen Schleicher, MD, is director of the DermDox Dermatology Centers, associate professor of medicine at Geisinger Commonwealth Medical College, and clinical instructor of dermatology at Arcadia University and Kings College.
References
1. Park S, Yun SJ. Acral melanocytic neoplasms: a comprehensive review of acral nevus and acral melanoma in Asian perspective. Dermatopathology (Basel). 2022;9(3):292-303. doi:10.3390/dermatopathology9030035
2. Palicka GA, Rhodes AR. Acral melanocytic nevi: prevalence and distribution of gross morphologic features in white and black adults. Arch Dermatol. 2010;146(10):1085-1094. doi:10.1001/archdermatol.2010.299
3. Saida T, Koga H, Uhara H. Dermoscopy for acral melanocytic lesions: revision of the 3-step algorithm and refined definition of the regular and irregular fibrillar pattern. Dermatol Pract Concept. 2022;12(3):e2022123. doi:10.5826/dpc.1203a123
4. Kim NH, Choi YD, Seon HJ, Lee JB, Yun SJ. Anatomic mapping and clinicopathologic analysis of benign acral melanocytic neoplasms: a comparison between adults and children. J Am Acad Dermatol. 2017;77(4):735-745. doi:10.1016/j.jaad.2017.02.041
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