Giant costal osteochondroma in a man with multiple exostoses.

We report the case of a 42-year-old man who presented with kyphosis resulting from a giant symptomatic costal osteochondroma around the left fourth rib. The osteochondroma on the left side of the back was 56 cm × 47 cm × 33 cm and was painful. The size and growth of the tumor suggested a malignant transformation of a large costal osteochondroma. Multiple osteochondromas were also found on the legs. The patient's family history revealed hereditary characteristics. This patient was clinically diagnosed as a case of multiple familial osteochondromatosis. Complete removal of the tumor relieved the symptoms, and histopathologic examination confirmed malignant transformation of chondrosarcoma. There was no recurrence after 16 months of follow-up.