RESUMO
Extraskeletal or soft-tissue osteosarcoma is rare, occurring approximately as 1.2% of all soft-tissue sarcomas and 4% of all osteosarcomas. The peak occurs in patients, which are in the 6th decade of life. The males are slightly more frequently affected. Symptoms often include a slowly growing painful mass, with a history of trauma [1 2% of cases]. Common sites of involvement are the deep soft tissues of the thigh [47% of cases], upper extremity [20%], and retropcritoneum [17%]. The identification of neoplastic osteoid matrix formation and aggressive characteristics are necessary for histological diagnosis of osteosarcoma. We are going to discuss 06 cases of extraskeletal osteosarcomas including primary renal, primary hepatic osteosarcoma, one arising in a cystosarcoma phylloides and 03 cases involving the thigh regions