Tumour-induced osteomalacia is a rare paraneoplastic syndrome caused primarily by benign mesenchymal tumors. These tumours typically follow a benign clinical course and local recurrence occurs in less than 5%. We investigated a 49-year-old man with multiply-recurrent mesenchymal phosphaturic tumor. The patient presented with chronic muscle weakness, myalgia and cramps. His medical record included the diagnosis of oncogenic osteomalacia for which he was submitted to tumor resection in the left leg thrice before. Laboratory examination showed hypophosphataemia, hyperphosphaturia, and an elevated serum FGF23 level. Radical surgical approach (amputation to the level of the distal femur) was recommended due to the tumour-size and history of previous recurrences. Complete biochemical and clinical remission, however, was not achieved. Molecular analysis of the tumour cells demonstrated overexpression of growth factor receptors implicated in tumour angiogenesis (PDGFRA, PDGFRB and VEGFR) together with increased expression of FGF23 and PHEX. TIO is usually associated with benign phosphauturic tumours and when identified resection of the tumour leads to complete remission. The underlying pathophysiology of recurrences in these tumours is not known. This is the first report showing increased expression of growth factor receptors in a locally aggressive but histopathologically benign phosphaturic mesenchymal tumour.
Disclosure: The authors declared no competing interests.