Meningeal Melanocytoma - Focus on Molecular Aspects with 3 New Molecular Alterations: A Literature Review and Report of Two Cases

Author(s): Axel de BERNARDI, Maureen BERNADACH, Judith PASSILDAS-JAHANMOHAN, Julian BIAU, Jean-Louis KEMENY, Xavier DURANDO

Background: Meningeal melanocytoma (MM) is a locally aggressive, low-grade primary melanocytic tumor of the central nervous system (PMN-CNS). According to the literature, GNAQ and GNA11 mutations are relatively frequent. In contrast, BRAF and NRAS mutations are very rare. Other series have reported BAP1 mutation, monosomy 3 and gain of chromosome 6. In this paper, we discussed two cases of MM for whom a FoundationOne CDxTM assay was performed.

Results: Case report 1: A 48 year old man was diagnosed with intermediate-grade MM based on histological assessment, which is consistent with the clinical evolution. The FoundationOne CDxTM assay detected a SF3B1 mutation, usually found in 15% of uveal melanomas. This mutation is correlated with improved progression-free survival in uveal melanomas. Case report 2: A 39 year old women was diagnosed with MM. Her evolution wasn’t expected based on histology only; her history didn’t match with rather benign histological features microscopically. The FoundationOne CDxTM assay provided two interesting elements: first, the tumour was positive for CDKN2A p16INK4a M52fs*1 and p14ARF H66fs*106 mutations, most commonly found in cutaneous melanomas. Secondly, a GNA11 Q209L mutation, known to be a marker of aggressiveness in uveal melanoma, was detected.

Conclusion: The identification of molecular alterations in PMN-CNS, in addition to immunohistochemical analysis could provide a better understanding of the biological and clinical behaviour of these tumours, a better identification of melanocytic melanomas with poor prognosis and a high risk of relapse or metastasis, and the development of novel therapeutic options for these patients.

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