Abstract

Malignant rhabdoid tumor (MRT) is a rare and highly aggressive neoplasm of infancy and childhood. Although it was originally described and most frequently reported in the kidney, it may occur in various extra-renal sites such as the liver, thymus, and soft tissue. In the last decade primary central nervous system (CNS) MRTs have been reported in both the supra- and infratentorial compartments. Patients with CNS MRT were generally below the age of two and reports in adults are extremely rare. This is a case of primary cerebellar MRT in a 24-year-old woman, who had presented with intermittent headache, vocal cord palsy, and cerebellar dysfunctions such as abnormal finger to nose test and tandem gait. By magnetic resonance imaging scan, a well-enhancing solid mass was demonstrated at the posterior fossa filling the 4th ventricle, which extended into the medulla and cervical cord via the foramen of Magendie. Histologically, the monotonous polygonal tumor cells were arranged in diffuse sheet with occasional hemorrhagic necrosis. The nuclei were vesicular and eccentrically located due to eosinophilic, PAS-positive, intracytoplasmic inclusions with prominent nucleoli. They were diffusely or focally immunoreactive for vimentin, neurofilament, cytokeratin, GFAP, synaptophysin, and smooth muscle actin, while epithelial membrane antigen and desmin were negative. Ultrastructurally, the polyhedral tumor cells were densely packed with primitive intercellular junctions. Scanty fibrillar intermediate filaments were intermingled with cellular organelles. Postoperatively, craniospinal irradiation and systemic chemotherapy have been done and she has been free of tumor recurrence during the 13 months' follow-up periods.

• Keywords: Malignant rhabdoid tumor;Central nervous system;Adult