 The tumors that cause oncogenic osteomalacia TIO express and release in the circulation phosphaturic factors such as fibroblast growth factor-23 FGF-23 that decrease renal phosphate absorption through acting in the proximal renal tubule and decreasing Type 2a and 2c sodium-phosphate co-transporter. They typically follow a benign clinical course and even in the rare malignant cases, local recurrence occurs in less than 5 and distant metastasis are very uncommon. 