[Epitheloid osteosarcoma. Differential diagnostic problems]

The case of a 23-year-old female patient suffering from a rare variety of osteosarcoma of the distal femur with epithelial differentiation and only traces of osteoid is reported. The tumour cells reacted strongly to antibodies against vimentin. Metastases were found in the fifth rib and the right kidney. There was no response to chemotherapy. One year after implantation of a tumour prosthesis of the knee a thigh amputation was necessary because of a local failure. The patient died 2.5 years after the tumour had initially been diagnosed. Other reports of this rare type of epitheloid osteosarcoma illustrate the difficulties involved in reaching a correct diagnosis. This tumour can be mistaken for a skeletal metastasis of an epithelial tumour.