Congenital spindle cell rhabdomyosarcoma.

Spindle cell and sclerosing rhabdomyosarcoma (ssRMS) is a rare variant of rhabdomyosarcoma, which includes three distinct subtypes. In infants, these tumors are commonly associated with recurring fusions involving VGLL2 or NCOA2 and have a favorable prognosis. We present four cases of ssRMS and 16 additional cases from the literature, which show that these patients present with localized disease and have an excellent prognosis regardless of surgical margin or lack of radiation therapy. Molecularly defined spindle cell rhabdomyosarcoma in infants is likely a biologically distinct entity which may not require the aggressive multimodal treatment used for other subtypes of rhabdomyosarcoma.