Chondromyxoid fibroma of bone: thirty-six cases with clinicopathologic correlation.

A series of 36 cases of chondromyxoid fibroma (CMF) of bone, a rare benign tumor that may be confused with chondrosarcoma, is presented to aid in correctly identifying and diagnosing these neoplasms. In this series, CMFs were found in patients of all age groups, with no predominance between sexes. Long bone tumors were more common in young patients, while small and flat bone lesions were more common in older patients. Radiographically, long, flat, and small bone lesions were well-defined and benign-appearing. Tumors in the vertebrae had a more aggressive appearance, with marked bone destruction. The histologic picture was of a pseudolobulated tumor with myxoid and chondroid regions. Tumor cells were at times bizarre, pleomorphic, and binucleate, but rarely contained mitoses. Curettage with or without bone grafting and en bloc resection were the most common modes of treatment. The majority of recurrences were seen in patients treated by curettage alone. Radiation therapy was associated with the development of sarcoma in one case. No cases of malignant transformation were found in this series, but unusually aggressive recurrences were noted in CMFs involving a phalanx, the cervical vertebra, and the sacrum.