Cytomorphology and immunohistochemistry of extrarenal rhabdoid tumor: a case report with review of literature.

Extrarenal rhabdoid tumor (ERRT) is a rare, aggressive tumor with extremely poor prognosis. We report a case of ERRT with intraspinal extension in a 1.5-year-old child diagnosed by fine needle aspiration cytology (FNAC) and immunohistochemistry. The child presented with a right lumbar region lump of two months duration. Ultrasound guided FNAC was performed and cell block was prepared. Smears were highly cellular and showed a dispersed population of large round cells having abundant pale eosinophilic cytoplasm, centrally to eccentrically placed nucleus with large prominent nucleoli. Immunohistochemistry was carried out on cell block which was positive for epithelial membrane antigen EMA and Vimentin. It was negative for leucocyte common antigen [LCA], wilms tumor 1, WT1, desmin and neuron specific enolase NSE, thus ruling out other tumors like lymphoma, Wilms tumor, rhabdomyosarcoma, and neuroblastoma. A final diagnosis of ERRT was given. ERRT is an extremely rare tumor of retroperitoneal area; it should be included in the differential diagnosis of malignant round cell tumor in children. Cell block in this case is mandatory for putting up the panel of immunohistochemistry which can clinch the diagnosis of rhabdoid tumor and treatment can be started as early as possible.