Cerebellar Liponeurocytoma, an Unusual Tumor of the Central Nervous System--Ultrastructural Examination.

Cerebellar liponeurocytoma is a rare tumor of the central nervous system which shows neuronal and variable astrocytic differentiation, along with foci of lipomatous differentiation. It is usually located in the cerebellum, and may be mistaken for medulloblastoma with lipidized cells or lipomatous ependymoma. Histopathological examination, supplemented by immunohistochemistry and electron microscopy, is required to distinguish between these entities. This 35-year-old male presented with vomiting and headache for three months, followed by gait imbalance. Neurological examination showed positive cerebellar signs with ataxic gait. Magnetic resonance imaging showed a lesion measuring 4.4 cm× 4.3 cm× 3.9 cm involving the cerebellum. The patient underwent midline suboccipital craniotomy to excise the tumor. Histopathological examination showed a circumscribed, cellular tumor composed of round to polygonal cells with moderate cytoplasm and minimal pleomorphism. Clear intracytoplasmic vacuoles were seen within the tumor cells. These tumor cells were immunopositive for synaptophysin, NSE, and MAP-2, confirming their neurocytic origin. On ultrastructural examination, lipid vacuoles as well as dense-core neurosecretory granules were identified within these neurocytic cells, confirming the diagnosis of liponeurocytoma. No cilia, microvilli, or gap junctions were identified in the tumor cells, ruling out the possibility of lipomatous ependymoma. The differentiation of liponeurocytoma from its morphological mimics is imperative, as their treatment differs drastically. The role of electron microscopy is extremely important in this differential diagnosis.