Rhabdoid features in leiomyosarcoma of soft tissue: With special referenceto aggressive behavior

The presence of rhabdoid cells has been reported in various types of malign ant neoplasms and has been determined to be a predictor of aggressive behav ior of neoplasms regardless of tumor histogenesis. One hundred and thirteen cases of leiomyosarcoma, selected from 1800 soft tissue sarcomas, were rev iewed on hematoxylin and eosin sections, and immunohistochemical staining w hen available, and seven cases with rhabdoid features were retrieved. Clini copathologic differences were analyzed to compare between cases with rhabdo id features and those without rhabdoid features. In the seven cases with rh abdoid features, two were intra-abdominal, and the others arose in external soft tissues including muscle, subcutis, and cutis, Patient age ranged fro m 33 to 84 years, three were female, and four were male. Tumor size ranged from 3 to 22 cm, Clinical evidence showed no differences from those cases w ithout rhabdoid features. Histologically, one of the abdominal cases was ep ithelioid leiomyosarcoma. Two of the 7 cases were better subclassified as p leomorphic leiomyosarcoma, in which rhabdoid cells are diffusely scattered. In cases other than those with pleomorphic leiomyosarcomas, foci of anapla stic areas were observed, and collections of rhabdoid cells were present in those areas. Immunohistochemical examination of the cases confirmed myogen ic differentiation, and showed rhabdoid cells being positive for vimentin a nd desmin in the inclusion bodies, and diffusely so for muscle actin in the cytoplasm, After dividing all the cases of leiomyosarcoma by their locatio n, prognostic analysis was performed. Leiomyosarcoma of external soft tissu e with rhabdoid cells showed a tendency for poorer prognoses than cases wit hout rhabdoid features, On the contrary, retroperitoneal cases did not. Thi s study indicates that rhabdoid features are associated with aggressive bio logical behavior in leiomyosarcoma of the external soft tissue.