Spindle cell/sclerosing rhabdomyosarcoma of the sphenoid sinus with intracranial and orbital extension: a rare case report with review of literature

Abstract Spindle cell/sclerosing rhabdomyosarcoma is a rare and aggressive subtype of rhabdomyosarcoma, and uncommon in the sphenoid sinus. We report a case of a 17-year-old male presented with bilateral facial swelling, headache, and visual blurring. Imaging showed an ill-defined, heterogeneously enhancing skull base mass involving the sphenoid sinus with intracranial and orbital extension, radiologically mimicking as esthesioneuroblastoma. Endoscopic endonasal debulking biopsy was suggestive of a spindle cell/sclerosing rhabdomyosarcoma on histopathological examination. Immunohistochemistry showed diffuse desmin and nuclear MyoD1 expression, and next-generation sequencing identified a MYOD1 p.Leu122Arg mutation, rendered the definitive diagnosis. The tumor was classified as FNCLCC grade G3, AJCC Stage III (T2b N0 M0), Intergroup Rhabdomyosarcoma Study Group (IRSG) Clinical Group III. Given the unresectable nature of the lesion, multimodal therapy including vincristine, actinomycin D (dactinomycin), and cyclophosphamide chemotherapy and proton beam radiotherapy was planned. Histology, immunohistochemistry, and molecular analysis are the cornerstones of the diagnostic planning process of this rare type of neoplasm. This case highlights the diagnostic challenges, aggressive behaviour, critical role of molecular testing and management protocols in Spindle cell/sclerosing rhabdomyosarcoma arising at an unusual skull base location.