Abstract
A 54-year-old man initially presented with left distal thigh pain during walking. Imaging analysis revealed a diffuse calcified or ossified mass adjacent to the medial cortex of the distal femur and absence of continuity with the medulla. We performed resection biopsy. Histological examination revealed a large amount of hypercellular cartilage showing transformation to trabecular bone and BPOP was diagnosed. Postoperative course was uneventful and he remained free of recurrence. The method of resection should depend on the stage of reactive proliferation and whether the lesion is pathologically immature or mature. We also provide a brief review of the literature.