Case report of secondary chondrosarcoma showing spontaneous regression after frequent recurrences

We report a case of secondary chondrosarcoma arising in the ilium showing s pontaneous regression after frequent local tumor recurrences followed by mu ltiple surgeries of marginal ol intralesional excision. The patient was a 1 6-year-old boy who had been diagnosed as having multiple exostosis from 9 y ears of age. He experienced an increasing abdominal tumor mass that formed a huge tumor. Although marginal resection of the tumor was attempted intrap eritoneal dissemination was caused by rupture of the tumor capsule and the peritoneum, as a result of severe tumor adhesion to the peritoneum. During the 5 years after the initial operation, local recurrences occurred seven t imes in. various ar eas of the intra- or retro-peritoneum and marginal or i ntralesional excision was performed every time for a total of 14 tumors. Ho wever; since the seventh operation, the patient has had no evidence of recu rrence or metastasis of the disease for more than 10 years Therefore, we co nsidered that the cancer might have spontaneously regressed.