Tumor-Induced Osteomalacia Mimicking Metastases on Ga-68 DOTATATE Scan: A Rare Pericytic Variant of Phosphaturic Mesenchymal Tumor.

Oncogenic osteomalacia (OOM), also known as tumor-induced osteomalacia (TIO), is a rare paraneoplastic syndrome caused by excessive production of fibroblast growth factor 23 (FGF23) by mesenchymal tumors. This leads to renal phosphate wasting, hypophosphatemia, decreased 1,25-dihydroxy vitamin D levels, and impaired bone mineralization. Patients often present with progressive muscle weakness, diffuse bone pain, and recurrent fractures, with symptoms frequently preceding diagnosis by several years due to the non-specific nature of hypophosphatemia and its exclusion from routine laboratory panels. We present the case of a 63-year-old man with a seven-year history of progressive musculoskeletal symptoms and multiple fractures. Despite extensive prior evaluations, his diagnosis was delayed until advanced imaging with Ga-68 DOTATATE PET/CT identified a somatostatin receptor-positive lesion in the right superior pubic ramus. Histopathological analysis confirmed a pericytic neoplasm, a rare histologic variant of phosphaturic mesenchymal tumor, consistent with the etiology of OOM. Laboratory evaluation demonstrated profound hypophosphatemia, elevated FGF23 levels, and reduced 1,25-dihydroxy vitamin D. Given the patient's elevated surgical risk, percutaneous cryoablation of the tumor was performed, resulting in normalization of serum phosphate levels and resolution of clinical symptoms. This case highlights the diagnostic challenges associated with OOM, the utility of somatostatin receptor-based PET/CT in tumor localization, and the importance of considering TIO in patients with unexplained hypophosphatemia and osteomalacia. Prompt recognition and surgical intervention can lead to complete resolution of symptoms and prevent long-term skeletal complications.