Track: Case Reports

Topic: Melanocytic Neoplasms

Abstract:

A 38-year-old male with a history of prolactinoma presented with a non-pigmented 4 cm nodule on the upper back. A shave biopsy revealed an atypical dermal melanocytic proliferation. Gene expression profiling results suggested a benign melanocytic neoplasm (score -13.0), but given the concerning features, excision was recommended. The excision revealed an atypical dermal-based spindle-to-epithelioid proliferation of cells arranged in sheets and fascicles extending into the subcutis. Verocay body-like configuration and scattered melanin pigment deposition were present. Atypia (large pleomorphic nuclei, prominent nucleoli, and mitotic activity (8 per mm2)) was identified. The cells were diffusely immunoreactive for SOX-10 and S100 and showed patchy expression of HMB45, Mart-1, and SMA and were negative for PRAME, CD56, pan-cytokeratin, p63, desmin, calretinin, ALK–1 and BRAF V600E. Chromosomal microarray demonstrated loss (monosomy) of chromosomes 2, 5, 9, 14, 17 and 22, plus loss of the short (p) arms of chromosomes 8 and 11. Next-generation sequencing demonstrated NRAS mutations and methylation classified the proliferation as melanoma. Given the additional molecular results, the diagnosis of melanoma with high-risk biologic potential was rendered. A re-excision with lymph node biopsies was performed, and the patient was found to have metastatic melanoma to one lymph node. The patient is being followed with no evidence of additional metastatic disease at the 6-month follow-up. We present this case to bring awareness that different molecular modalities may generate different results, and these results should always be interpreted in the context of histopathologic findings.

Michael Schild

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(Virtual) Molecular Tests in Challenging Melanocytic Tumors: A Case Study