Acral melanoma in situ displaying a "regular" fibrillar pattern on dermoscopy

"Regular" fibrillar pattern seen in acral melanoma in situ.

(A, inset) Clinical features – A brown patch, 13.5 × 10.5 mm in size, seen on the sole of a 78-year-old female patient.

(A) The very thin fibrils constituting this fibrillar pattern are evenly arranged and regular in color and thickness.

(B) The square area in panel A. The furrow ink test reveals that the sulci of the skin markings, indicated with arrowheads, are spared from the fibrillar pigmentation.

(C, D) Histopathologic features. Panel D corresponds to the square area in panel C. The thick cornified layer is obliquely arranged (as indicated with arrows in panel C). The increased number of melanocytes are mainly detected in the crista profunda intermedia (indicated with asterisks in panel C), and their nuclei are large and hyperchromatic (as seen in panel D), confirming this is acral melanoma in situ. (NOTE: FISH analysis of this lesion revealed amplification of cyclin D1.)