Periosteal chondroma of the ischium; an unusual location

Periosteal chondroma is a rare benign tumor of hyaline cartilage. Periosteal chondroma arising in the ischium is an extremely rare event. By presenting this case report, we aim to remind that differential diagnosis of these lesions should be carefully performed especially for unusual locations. A 51-year-old man visited the orthopedics clinic with the complaints of left pelvic mass and pain lasting about one year. Computed tomography showed a solid mass with abundant specks of calcification that was 4x5 cm in diameter and associated with the ischium of the left pelvic bone. There was no evidence of penetration into the medullary cavity and cortical sclerosis. No radiological aggressive appearance was observed. The lesion was removed with the covering periosteum. Microscopically, there were lobules of hyaline cartilage composed of chondrocytes with foci of endochondral ossification and calcification. The case was reported as 'periosteal chondroma'. In conclusion, this case report presents a case of periosteal chondroma, a rare tumor, which occurred in an unusual location and age range. The differential diagnosis of periosteal chondroma from malignant lesions is necessary for avoiding aggressive and inappropriate treatment.