[Metastasized osteosarcoma with undifferentiated carcinoma-like parts].

This was the case of a 64-year-old man with osteosarcoma. The biopsy yielded undifferentiated tumor without bone or cartilage formation. Because of high age of the patient and radiological changes present, a metastatic carcinoma was suspected. However, no primary could be found. Autopsy revealed an osteosarcoma in the region of the hip joint with alternating formation of tumor cartilage and tumor bone. There were also undifferentiated portions of "endocrine osteosarcoma," simulating carcinoma. In spite of extensive skeletal involvement and pulmonary metastases--and high age--no evidence of morbus Paget of bone as possible preneoplastic disease was found.