A case of malignant rhabdoid tumor mimicking yolk sac tumor.

Malignant rhabdoid tumors (MRTs) are rare, highly aggressive embryonal neoplasms caused by biallelic alterations of the SMARCB1 gene. MRTs may occur in any soft tissue, but extracranial extrarenal MRTs are extremely rare. Diagnosis of MRTs in unusual locations and with an uncharacteristic cytomorphology that mimics other tumors is difficult. This was an atypical case of MRT in a 15-year-old female with tumors that closely resembled yolk sac tumors. It was extremely challenging to diagnose the tumors without confirming the SMARCB1 status.