P14.24.A CLINICAL, HISTOPATHOLOGICAL AND MOLECULAR FEATURES OF FOUR CASES OF MENINGEAL MELANOCYTOMA

Abstract BACKGROUND Meningeal melanocytoma is a rare primary melanocytic tumor of the central nervous system. Due to its low incidence, clinicopathological and molecular data remain limited. We present a series of four cases to highlight the spectrum of clinical and morphological features, the immunohistochemical profile with varying proliferative activity, and specific genetic alterations. MATERIAL AND METHODS We retrospectively reviewed four cases of meningeal melanocytoma diagnosed at our institution over the past 10 years. Histological examination and immunohistochemistry were performed in all cases. In one recent case, DNA-based next-generation sequencing (NGS) was also conducted. Clinical follow-up data were obtained from the hospital records. RESULTS The patients ranged in age from 36 to 73 years and included two males and two females. Tumor locations were the thoracic spinal cord (n=1), pineal region (n=1), basal temporal region (n=1), and unspecified supratentorial meninges (n=1). The tumors were hypercellular, composed of oval to spindle-shaped or epithelioid cells. All tumors showed at least focal melanin pigmentation. Immunohistochemistry was positive for S100 and HMB45, and negative for EMA and cytokeratins in all cases. The Ki-67 proliferation index ranged from 1% to 15%. In the most recent case, occurring in a 73-year-old woman, NGS revealed a GNA11 p.Q209L mutation. Follow-up data were available in all cases, with durations ranging from 1 to 7 years. Local recurrence occurred in two of these cases, both three years after the initial therapy. None of the patients died of the disease during the follow-up period. CONCLUSION Our series illustrates the histological and immunophenotypic consistency of meningeal melanocytomas across a broad age spectrum and various CNS locations. The variability in proliferative activity and the occurrence of delayed local recurrence despite multimodal therapy highlight the tumor’s intermediate biological potential. Molecular testing may support the diagnosis and aid in excluding metastatic melanoma. FUNDING Research Project of the Ministry of Health of Czech Republic No. 00064203.