Malignant extrarenal rhabdoid tumor: a case report.

BACKGROUND: Malignant extrarenal rhabdoid tumor is a rare and aggressive soft tissue sarcoma that typically affects infants. It poses considerable diagnostic challenges owing to its overlap with other tumors showing rhabdoid features. CASE PRESENTATION: A 6-year-old Indian girl presented in our institute with a gluteal mass arising from the sciatic nerve. Histopathology showed rhabdoid morphology with cytoplasmic inclusions. Immunohistochemistry revealed diffuse epithelial membrane antigen and vimentin positivity, variable cluster of differentiation 99, and loss of integrase interactor 1, consistent with malignant extrarenal rhabdoid tumor. Differential diagnoses-including epithelioid sarcoma, malignant peripheral nerve sheath tumor, chordoma, and Capicua transcriptional repressor gene-rearranged sarcoma-were ruled out based on immunohistochemistry. The patient underwent wide local excision, postoperative radiation (60 Gy), and adjuvant chemotherapy. Despite treatment, she developed foot drop and local skin necrosis, which was managed surgically. CONCLUSIONS: This case underscores the importance of recognizing distinct features of malignant extrarenal rhabdoid tumor to ensure accurate diagnosis and early intervention, as the disease remains aggressive with a high risk of recurrence despite multimodal therapy.