Histopathologic features of early acral melanoma

Histopathologic features of the macular portion of an acral melanoma showing the parallel ridge pattern on dermoscopy.

(A) Melanocytes arranged as solitary units are mainly observed in the crista profunda intermedia (asterisks), although a few melanocytes are also detected in the crista profunda limitans (arrows) (hematoxylin and eosin stain).

(B) Melanin granules in the cornified layer are mostly derived from melanocytes in the crista profunda intermedia (Fontana-Masson stain). They are detected as broad columns under the surface ridges (blue bars). Melanin granules are mostly absent in the cornified layer under the surface furrow, corresponding to the underlying crista profunda limitans (arrows). This distribution corresponds well to the dermoscopic parallel ridge pattern.