Track: Case Reports

Abstract:

Background: Vulvar mucosal melanoma is a rare, aggressive malignancy with distinct molecular features. While KIT, NRAS, and BRAF mutations are commonly described, alterations involving CDKN2B, MTAP, and TERT promoter mutations are less characterized in this site.

Materials and Methods: An adult female with a history of treated breast carcinoma and chronic reflux presented with a vulvar lesion initially treated as a fungal infection without improvement. Biopsy confirmed melanoma with lesion enlargement and intermittent bleeding near the clitoral area. She was scheduled for a vulvectomy. Histopathology showed poorly differentiated spindle and epithelioid tumor cells. Immunohistochemistry performed externally was negative for p16, chromogranin, Ber-EP4, cytokeratin 5/6, synaptophysin, p40, and AE1/AE3. Additional staining at a tertiary center showed strong positivity for Melan-A, S100, and SOX10. Molecular testing revealed CDKN2B homozygous deletion, MTAP exon 3 p.P105 mutation, and TERT promoter c.- 124C; T mutation. No KIT, NRAS, or BRAF mutations/deletions were detected. Microsatellite stability was confirmed.

Results: The immunophenotype confirmed melanocytic differentiation and excluded carcinoma and neuroendocrine neoplasms. The molecular profile suggests a high-risk subtype given associations of CDKN2B and MTAP deletions with aggressive melanoma and TERT promoter mutations with poor prognosis.

Conclusions: This case represents a rare molecular subset of vulvar melanoma with diagnostic and prognostic significance. It highlights the importance of molecular profiling in mucosal melanomas, especially in patients with synchronous malignancies.

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Xiaoyu Tang