Nasal hemangiopericytoma presenting with oncogenic osteomalasia: A case report and literature review.

Sinonasal type hemangiopericytoma is a rare soft tissue tumor. Oncogenic osteomalacia (tumor-induced osteomalacia) is a rare syndrome that develops especially due to benign mesenchymal tumors. Nonspecific general bone pain and weakness delay the diagnosis and treatment of oncogenic osteomalacia, and it is difficult to determine the localization of the primary tumor causing oncogenic osteomalacia. A 43-year-old male patient with nasal hemangiopericytoma with symptoms of oncogenic osteomalacia is presented. The patient had musculoskeletal complaints at first and was diagnosed with lumbar disc herniation and surgery was performed. When his complaints recurred 1 year later, he was re-evaluated and diagnosed with hypophosphatemic osteomalacia. Despite the various treatments he received, his complaints did not decrease but increased, so a detailed examination was decided. When the positive PHEX mutation and very high fibroblast growth factor 23 level were detected, PET-CT imaging was performed with a pre-diagnosis of possible oncogenic osteomalacia, but no finding was found. Then he was evaluated with Ga-68 DOTATATE, and the soft tissue mass filling the right ethmoidal sinus was detected. Due to the relation of the mass with surrounding structures, it was considered unsuitable for total excision and incomplete surgical excision was performed. Pathologic evaluation revealed sinonasal type hemangiopericytoma (glomangiopericytoma). A significant remission in the patient's complaints was observed after the operation. Young patients with osteomalacia with unknown causes should be evaluated for malignancy, and screening and further examinations should be performed.