1. To provide an overall view of the phosphate homeostasis 2. To provide an overall view of the pathophysiology, epidemiology and presentation of phosphaturic tumors that result in oncogenic osteomalacia (OO) 3. To review the imaging features of phosphaturic tumors 4. To present the variety of imaging findings from fifteen cases of phosphaturic tumors.

See attached slides BACKGROUND Mechanisms of phosphate homeostasis Phosphate plays an important role in skeletal development, bone mineralization. Phosphate levels are maintained through renal tubular and intestinal reabsorption and through exchange with intracellular and bone storage pools. Hypophosphatemia stimulates 1,25 dihydroxy Vitamin D synthesis by the kidney Results in increased serum calcium and phosphate via mobilization from bone. In response, parathyroid hormone (PTH) is reduced while calcium excretion and phosphate reabsorption are increased. Phosphate is filtered through the glomerulus with 80% reabsorbed in proximal tubule...

See attached slides IMAGING FINDINGS Epidemiology Patient Population Mostly adults over the age of 30 years Slight male predominance (male to female ratio of 1.2). Oncogenic osteomalacia may, however, be observed from childhood to the eighth decade of life (7 to 73 years of age). Can occur anywhere in the body Predilection for craniofacial and lower extremity locations Phosphaturic lesions are frequently small and difficult to detect A broad spectrum of tumors can result in OO Most commonly: Vascular lesions such as hemangiopericytomas Mesenchymal tumors...

The viewers will be familiar with phosphaturic mesenchymal tumors with the following take-home points: 1.OO, an uncommon paraneoplastic disorder, is related to phosphaturic lesions mostly composed of hemangiopericytomas and mesenchymal tumors. 2.Its pathophysiology rests on tumor-released phosphaturic phosphatonins such as FGF-23, which is a useful tumor maker for OO diagnosis and posttherapeutic surveillance. 3.Hypophosphatemic disorders XLH and ADHR share intricate FGF-23, PHEX and MEPE pathways of phosphate wasting disorder and represent potential differential diagnosis of OO in young patients. 4.Even with an established diagnosis of...

Avila NA, Skarulis M, Rubino DM, Doppman JL. Oncogenic osteomalacia: lesion detection by MR skeletal survey.AJR Am J Roentgenol. 1996;167:343-5. Carpenter TO. Oncogenic osteomalacia – a complex dance of factors. N Engl JMed. 2003;348:1705-8. Chalew SA, Lovchik JC, Brown CM, Sun CC. Hypophosphatemia induced in mice by transplantation of a tumor-derived cell line from a patient with oncogenic rickets. J Pediatr Endocrinol Metab. 1996;9:593-7 Dupond JL, Mahammedi H, Prie D, et al. Oncogenic osteomalacia: diagnostic importance of fibroblast growth factor 23 and F-18 fluorodeoxyglucose PET/CT...