Bifocal cerebellar liponeurocytoma with atypical features: A case report and a literature review.

Cerebellar liponeurocytoma (cLNC) is a rare tumor. It affects adults with no sex predilection. It appears as a heterogeneously enhancing mass, most commonly unifocal. Histologically, it is a biphasic neurocytic tumor with lipomatous component, with minimal atypia, and low proliferative index, corresponding to central nervous system (CNS) World Health Organization (WHO) grade 2. TP53 missense mutation is reported in 20% of cases. Gross total resection, with or without radiotherapy, is considered an adequate treatment. Bifocality and features of anaplasia are rarely reported. We are reporting a 41-year-old lady with bilateral cerebellar contrast-enhancing masses who underwent gross total resection 3 months apart. Pathology revealed features consistent with cLNC. However, the tumor resected from the right cerebellar hemisphere demonstrated atypical morphological features, including microvascular proliferation and necrosis. Ki-67 proliferative marker was estimated at 10% in the most active areas. Next-generation sequencing (NGS) revealed 2 pathogenic mutations within exonic regions of ERBB2, and PIK3CA genes, and a variant mutation of unknown significance (VUS) involving the PDGFRA gene. DNA methylation profiling confirmed the diagnosis of cLNC. The patient has been under observation without any further intervention for 70 months since diagnosis, with no evidence of disease recurrence. In addition to the rarity of cLNC, this is a unique case in terms of bifocality, anaplastic histology, and the described genetic abnormalities.