Unexpected Phosphaturic Mesenchymal Tumor of the Femoral Head.

Osteonecrosis of femoral head (ONFH) is clinically common and easily diagnosed via imaging examination, especially when there is a definite cause, such as a fracture, long-term hormonotherapy, etc. However, some rare neoplastic lesions of the femoral head can mimic its image performance in some situations, leading to misdiagnosis. We present the case of a 57-year-old male with bone pain in the left hip joint that persisted for 2 years. CT and MRI images were performed and both were suggestive of ONFH. Unexpectedly, the histopathologic results of left proximal femur resection revealed the diagnosis of phosphaturic mesenchymal tumor (PMT), a rare mesenchymal tumor. His hip pain was obviously relieved after surgery, and the course of 1-year follow-up was uneventful.