A Case of Temporal Bone Phosphaturic Mesenchymal Tumor That Was Treated by Surgery

Phosphaturic mesenchymal tumor (PMT) is a rare neoplasm that secretes fibroblast growth factor 23 (FGF23), which suppresses re-absorption of phosphorus in the renal tubules and leads to chronic hypophosphatemia, thereby resulting in tumor-induced osteomalacia (TIO). Herein, we report a patient who had suffered multiple fractures and was diagnosed as having PMT in his left temporal bone two years later the appearance of the first symptom. For his first consultation at our department, the patient was transported to the hospital on a stretcher, as he had found it difficult to turn over in bed due to generalized bone pain and multiple pathological fractures. Examination revealed that the tumor had already spread deep into the skull base; therefore, considering the general condition of the patient, we determined that radical surgery would be difficult. Transmastoid surgical debulking was performed three months after the first consultation at our department, and the patient’s quality of life improved after the surgery. However, 10 months after the surgical debulking procedure, since we did not observe any improvements in his clinical findings, we performed radical surgery together with the neurosurgeons, which yielded good results. This case suggests that radical surgery is essential for the treatment of PMT. Even in cases where radical surgery is initially deemed to be challenging, gradual steps towards radical surgical treatment may be possible.