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Published online by Cambridge University Press: 10 July 2025
Background: Primary melanocytic neoplasms of the central nervous system (PMN-CNS) are rare lesions of variable aggressiveness originating from leptomeningeal melanocytes. They present as either circumscribed or diffuse lesions within the CNS. Given the limited number of reported cases, survival and recurrence outcomes are poorly understood. Methods: A retrospective chart review of all local adult (≥18 years) cases of PMN-CNS in British Columbia, Canada (1993-present). Results: We identified 11 cases, median age at diagnosis was 60 years (IQR: 45-64), 72% female. Tumor location included cerebrum (54.5%), spine (36.4%) and multifocal (9.1%). Four cases (36%) had confirmed GNAQ/GNA11 mutations and six cases (54.5%) were negative for BRAF V600E mutations. Operative outcomes were: gross total resection (27.3%), subtotal resection (63.6%) and biopsy-only (9.1%). Surgery was followed by adjuvant fractionated radiotherapy in 10 (91%) cases. Seven cases (63.6%) received adjuvant chemotherapy and/or immunotherapy, specifically ipilimumab and nivolumab (n=6) and temozolomide (n=1). Radiographic recurrence was observed in 7 (63.6%) cases at a median 11 (IQR: 3.5-14) months postoperatively. Median survival was 24 months (IQR: 4-103). Conclusions: Findins from this case series will assist in prognostication for PMN-CNS. Further multicenter international case series are needed to better understand these very rare neoplasms.