Spindle cell/sclerosing rhabdomyosarcoma: case series from a single institution emphasizing morphology, immunohistochemistry and follow-up.

Spindle cell/sclerosing rhabdomyosarcoma is a rare skeletal-muscle tumor with distinctive clinicopathologic characteristics. 10 cases (6 cases of spindle cell rhabdomyosarcoma and 4 cases of scleroisng rhabdomyosarcoma) were composed of 6 males and 4 females aging from 5 months to 57 years, with median age 33 years, most of who represented a painless solid mass. Histologically, the tumors were composed of fascicles of spindle cells or primitive round cells embed in sclerotic matrix with presence of rhabdomyoblasts in varying proportion. Immunohistochemically, the tumor cells expressed MyoD1 (10/10), Desmin (10/10), myogenin (6/10), AE1/AE3 (2/10), EMA (2/10), but were negative for SMA, caldesmon, S-100. All of the patients underwent a complete surgical resection without or with chemotherapy (2/10) or radiotherapy (1/10). During the follow-up period (1 to 24 months), 1 patient was succumbed, and 2 cases showed in situ recurrence with 1 of them adopting metastasis. Our cases further demonstrate there do present some clincopathologic relations between spindle cells rhabdomyosarcoma and sclerosing rhabdomyosarcoma, but the latter seems to have a better prognosis. Exact grading and staging contribute to predict the outcome.