Malignant chondroblastoma presenting as a recurrent pelvic tumor with DNA aneuploidy and p53 mutation as supportive evidence of malignancy

We report a rare case of malignant chondroblastoma, which presented in a 47 -year-old man as a recurrent tumor, 18 years following wide excision of a t ypical pelvic chondroblastoma. Radiologic studies of the recurrent tumor sh owed a large, lytic, destructive lesion of the right pelvic bones and femur , with a pathologic fracture of the latter, a large pelvic soft tissue mass , and multiple pulmonary metastases. Biopsy tissue showed typical features of chondroblastoma, but also increased nuclear atypia, hyperchromasia, and pleomorphism, compared to the original tumor, and, most significantly, abno rmal mitotic figures. Immunohistochemical studies of the recurrent tumor re vealed p53 mutation and extensive proliferative activity, and flow cytometr ic studies showed DNA aneuploidy, none of which was present in the original tumor. The patient received chemotherapy and radiation, but died of diseas e eight months after presentation. We also review chondroblastoma in genera l, to assign this unusual lesion to a tumor subtype.