Acral Lentiginous Melanoma Developing during Long-standing Atypical Melanosis: Usefulness of Dermoscopy for Detection of Early Acral Melanoma

Abstract

Clinical guidelines suggest that suspicious pigmented lesions of the plantar or palmar area require biopsy for early detection of acral melanoma. We present here a case of acral lentiginous melanoma in which various melanocytic atypia was observed at each biopsy site, including focal melanocytic proliferation. We suggest that this atypical melanosis is part of a contiguous phase of invasive tumor growth, which is known as the very early stage of melanoma in situ. In addition, noninvasive dermoscopy has been effective for the early discovery of hidden lesions of acral melanoma.

Keywords: Acral lentiginous melanoma; Dermoscopy.

Fig. 1

A 1.5×0.8-cm hyperkeratotic patch with irregular border and variegated color on the left heel. The lesion was surrounded by a sharply demarcated brownish patch with some mottled dark pigmentation. Initial punch biopsy site (white arrow).

Fig. 2

Increase in basal melanocytes and hyperpigmentation with focally uniform, severe cytologic atypia of melanocytes (A: H&E, ×40, B: H&E, ×100, C: H&E, ×200).

Fig. 3

Typical parallel ridge pattern and abrupt cut-off of pigmentation observed upon dermoscopy.

Fig. 4

(A, B) Atypical melanocytes are nested at the upper dermis, with a Breslow thickness of 2.0 mm (A: H&E, ×40, B: H&E, ×200), (C) Melan A(-) (H&E, ×200), (D) HMB45(+, focal) (H&E, ×200), (E) S-100(+) (H&E, ×200).

Fig. 5

Histologic findings of peripheral brownish patch area, melanocytic proliferation predominantly in the crista profunda intermedia and diffuse basal hyperpigmenation (A: H&E, ×40, B: H&E, ×100, C: H&E, ×200).