Invasive Melanoma Arising From Basal Cell Carcinoma Passenger Melanocytes: Case Study
Posted: Tuesday, August 25, 2020
A case study reported in the Journal of Cutaneous Pathology described a skin tumor found on a 91-year-old man; invasive melanoma cells appeared to have originated from passenger melanocytes within a basal cell carcinoma. Brent Talbott, MD, and his colleague Hana Paladichuk, MD, both of The University of Texas at Austin Dell Medical School, Austin, shared their clinical experience with this rare case.
The patient presented with a 2-year history of a growing, painful, 2-cm ulcerated tumor on the helix of his right ear. When biopsy was performed on this lesion, histopathology revealed an invasive tumor with distinct but intertwined, basaloid and epithelioid components. The basaloid portion stained positively for cytokeratin markers, with classic features of basal cell carcinoma on presentation. However, the epithelioid component of the tumor did not stain with the basaloid markers and appeared as a separate entity from the basaloid portion, rather than a derivative.
Upon further investigation, the epithelioid cells were noted to be arising from within the basal cell carcinoma and simultaneously infiltrating the surrounding stroma. These cells had enlarged nuclei with prominent nucleoli and frequent mitotic figures. Staining of these cells was positive for the melanoma markers S-100, MART-1, and SOX-10. The MART-1 staining demonstrated dendritic morphology of the passenger melanocytes within the basal cell carcinoma and showed transformation into frank melanoma, with adjacent nondendritic clusters of epithelioid melanocytes. There appeared to be no connection between these malignant melanocytes and the overlying epidermis, suggesting this was an invasive melanoma without an epidermal or in situ component.
In addition, a separate area of chondroid differentiation was noted next to the invasive melanoma. Staining with SOX-1 revealed sheets of malignant melanocytes flanking the cartilaginous component, which stained positively for S-100 alone. The cells within the cartilaginous area showed striking nuclear atypia, suggesting transdifferentiation of the melanoma.
Disclosure: The authors reported no conflicts of interest.
