Symptoms will appear when these lesions become large enough to produce pain or discomfort.15 Although PMTs are the most common cause of TIO, several benign and malignant lesions can produce FGF-23, such as odontogenic fibroma, haemangiopericytomas, giant cell tumour of tendons and, in a minority of cases, phosphaturic malignant tumours.1,15. Here, FGF23 is linked to cancer.