Extraskeletal Osteosarcoma. Case report and differential diagnosis.

In this case of an extraskeletal osteosarcoma initially there were typical difficulties in diagnosing a) a malignant mesenchymal tumor and b) a bone-producing tumor. Only focally the test-booking findings of an osteosarcoma were present. The differential diagnosis concerned mainly pseudosarcomatous lesions with bone formations, which histologically may appear suspicious, however, follow a benign course clinically.