CS-1 Cerebellar liponeurocytoma; Report of two cases with detailed metabolic, immunohistochemical, and genetic evaluations

Cerebellar liponeurocytoma (cLNC), World Health Organization grade II neoplasm, is a rare brain tumor characterized by advanced neuronal/neurocytic differentiation and focal lipid accumulation in neuroepithelial tumor cells. However, the expression and genetic profiling of cLNC, as well as metabolic imaging characteristics, have been poorly studied. Two patients with lower vermian tumors were operated on with telovelar approach. Moderate methionine uptake in positron emission tomography was observed in both cases. Histologically, the tumor was composed of small, uniform cells with round nuclei in a sheet-like fashion. Vacuolate cells with displacement of nuclei suggested the lipid accumulation, which was further supported by immunohistochemical staining of S-100. Although the extent of lipidization was relatively low compared with the reported cLNC cases, the immunohistochemical findings confirmed the diagnosis of cLNC. Next-generation sequencing of tumoral DNA in one case detected a splice site mutation of the ATRX gene, which is the first observation in the literature. Neither chemotherapy nor radiotherapy were administered postoperatively in both cases. In one case with spinal dissemination, residual tumor demonstrated progression 7 months after the resection. Long term follow-up data of cLNC cases with detailed expression and genetic profiles are essential for precise diagnosis and better understanding of the oncogenic pathway as well as the natural history of cLNC.