Fibrous dysplasia arising from the calcaneus

A case of an 18-year-old woman with fibrous dysplasia arising in the calcaneus, which is extremely rare, is reported, with the emphasis placed on differential diagnosis from low-grade central osteosarcoma. She had a severe pain in her left ankle after sprain. Plain radiographs showed a radiolucent lesion measuring 6.3x2.5 cm with a sclerotic margin in the left calcaneus. CT scans showed a well-defined lytic lesion with disruption of the lateral cortex and an ossification or calcification in its center. On MR imaging, the lesion had isointensities and high intensities on T1 and T2 weighted images, respectively, but its central portions showed lower intensities both on T1 and T2 weighted images. The lesion was enhanced with gadolinium except for the central portions. The specimen obtained by open biopsy consisted of fibrous tissue and foci of irregular woven bone. None of the nuclear atypia, mitoses, longitudinal stream of bone or invasive nature of growth was detected. The diagnosis of fibrous dysplasia was histologically made. The lesion was curetted and packed with autogenous bone chips. No evidence of recurrence was noted postoperatively.