Atypical dermoscopic presentation of an acral congenital melanocytic nevus in an adult: parallel ridge pattern and its histologic correlation

Abstract

Acral melanoma is the most frequent subtype in the Asian and Mexican mestizo populations. Dermoscopy is a noninvasive diagnostic technique that helps the differential diagnosis of pigmented skin lesions on acral volar skin. We, herein, present a case of acral congenital melanocytic nevus with a parallel ridge dermoscopic pattern. Since the parallel ridge pattern in a melanocytic lesion of the acral skin is classically ascribed to melanoma, the present case can be definitely labeled as "atypical" and worth of being elucidated in its histopathological correlates.

Keywords: acral; congenital; dermoscopy; histopathology; nevi.

Figures. 1 and 2.

A 12 mm pigmented lesion on the plantar arch. [Copyright: ©2015 Roldán-Marín et al.]

Figures. 1 and 2.

A 12 mm pigmented lesion on the plantar arch. [Copyright: ©2015 Roldán-Marín et al.]

Figure 3.

Polarized dermoscopy revealed a polychromatic lesion with a central blue-grey area and dark and light brown colors in the periphery. A central parallel ridge pattern blended with a peripheral lattice-like pattern associated with few asymmetric dots and globules. The furrows at the periphery were relatively devoid of pigmentation. [Copyright: ©2015 Roldán-Marín et al.]

Figure 4.

(A) Histopatology (10× hematoxylin & eosin [H&E] stain) revealed a very bland compound melanocytic neoplasm with clear-cut congenital-like features. (B) (40× H&E stain) An intradermal combination of type C and dendritic (blue nevus-like) melanocytes. (C) (40× H&E stain) Striking acrosyringial and periductal distribution. (D) (20× H&E stain) Mainly peripheral regularly arranged melanocytic nests at the dermo-epidermal junction, but areas with melanin columns from melanocytes located in the crista profunda intermedia. (E) (40× H&E stain) Columnar melanin depositions (melanin columns) arrayed under the surface furrow. [Copyright: ©2015 Roldán-Marín et al.]