SECTION EDITOR: MARY S. STONE, MD; ASSISTANT SECTION EDITORS: SOON BAHRAMI, MD; CARRIE ANN R. CUSACK, MD; MOLLY A. HINSHAW, MD; ARNI K. KRISTJANSSON, MD; LORI D. PROK, MD
The biopsy specimen revealed a proliferation, with pagetoid spread, of atypical melanocytic epithelioid elements throughout the epidermis of the nail bed and the matrix (Figure 2). The patient refused finger amputation and underwent surgical removal of the dorsal part of the distal phalanx. Pathologic examination of the specimen revealed invasive tumor cells in the reticular dermis (Clark level IV), with a 0.9-mm Breslow thickness and without regressive phenomena or inflammatory infiltrate. Neoplastic cells proved to be strongly positive for HMB-45 (Figure 3) and weakly positive for S-100 protein and Melan-A. The mitotic rate, quantified with Mib/Ki67, was nearly equal to 2% to 3%. The dermal pattern of proliferation showed scattered solitary units, without nest formation, while in the epidermis, there were a few irregularly shaped nests (Figure 4). Sentinel lymph node excision was negative for metastatic melanoma, as was the total body scan.
Longitudinal Deep Fissure and Distal Onycholysis of the Right Thumb—Diagnosis. Arch Dermatol. 2012;148(8):947–952. doi:10.1001/archderm.148.8.947-e