Infantile rhabdomyofibrosarcoma: A potentially underdiagnosed aggressive tumor

Infantile Rhabdomyofibrosarcoma (IRMFS) is a rare clinicopathological entity that resembles infantile fibrosarcoma (IFS) but has ultrastructural and immunohistochemical evidence of rhabdomyoblastic differentiation. We report a 2 years and 6 months old boy who presented with a slowly progressive large soft-tissue mass in left axillary region. After complete excision, histopathology report revealed diagnosis of IFS. Review of the histopathology with immunohistochemistry (positive for desmin) revealed diagnosis of IRMFS. He was treated with aggressive adjuvant chemotherapy. He was in complete remission 6 months after completion of chemotherapy. In view of poor prognosis and aggressive treatment approaches for IRMFS, it must be differentiated from IFS to avoid under treatment.