Pigmented epithelioid melanocytoma (animal-type melanoma): An institutional experience

Background Pigmented epithelioid melanocytoma (PEM) is an uncommon, recently described entity with unknown biologic behavior. There is a high rate of regional metastases, but limited evidence of distant metastases or disease-related death. Objective We sought to report our series of patients given a diagnosis of PEM at our institution and provide mutational analysis of genes commonly implicated in melanoma in 2 cases. Methods The pathology database was queried for cases of PEM diagnosed at the University of Rochester. Charts were reviewed for follow-up information. Mutational analysis of melanoma-associated genes was performed on 2 cases. Results Nine cases of PEM were retrieved in a 10-year retrospective review. Five patients underwent sentinel lymph node biopsy with 3 of 5 having a positive sentinel lymph node. All 9 patients are alive and disease-free with average follow-up of 38.75 months. Two tumors were tested for common melanoma-associated mutations, and were negative, except for a telomerase reverse transcriptase promoter deletion detected in 1 sample. The deletion has not been associated with melanoma, and therefore its biologic significance is unclear. Limitations Small sample size, retrospective nature, and single institution experience are limitations. Conclusions PEM appears to have an indolent behavior. However, currently the evidence is too limited to provide insight into its true biologic potential.