Epidemiology
A rare tumor that can cause oncogenic osteomalacia through renal loss of phosphate. It must be suspected if there is diffuse bone pain, weakness, and low phosphate, because removing the tumor can correct the osteomalacia.
Basic features
It is often small and hard to locate; it overproduces the factor FGF23, which makes the kidney lose phosphate and causes an oncogenic osteomalacia with bone pain, weakness, and insufficiency fractures.
Usual treatment
Complete resection usually corrects the metabolic disorder; locating it may require functional imaging such as Ga-68-DOTATATE PET/CT, and when it cannot be located or removed, the antibody burosumab (anti-FGF23) helps correct the phosphate deficiency and the symptoms.
Outcomes and prognosis
The prognosis is very good if it is removed completely (most are benign and resection corrects the osteomalacia), but persistence or recurrence keeps the metabolic disorder going.