PHOSPHATURIC MESENCHYMAL TUMOR IN THE MANDIBLE WITH ASSOCIATED ONCOGENIC OSTEOMALACIA: A CASE REPORT

Abstract

Phosphaturic mesenchymal tumor (PMT) is a rare neoplasm that has been associated with oncogenic osteomalacia. This tumor secretes fibroblast growth factor-23 (FGF-23). Although other mesenchymal tumors can cause oncogenic osteomalacia, PMT is the most common mesenchymal neoplasm associated with oncogenic osteomalacia and accounts for 80% of such cases. Most patients are adults and the tumor can affect both men and women. The most common location for the tumor is the lower extremities followed by the head and neck area. Patients typically present with diffuse bone pain, bone fractures, and progressive muscle weakness. The laboratory studies usually reveal increased levels of FGF-23, hyperphosphaturia, increased alkaline phosphatase, normal serum calcium and parathyroid hormone levels, normal to low levels of 1,25-dihydroxyvitamin D and hypophosphatemia. The four common phosphaturic mesenchymal tumor microscopic subtypes are: phosphaturic mesenchymal tumor mixed connective tissue variant (PMTMCT), osteoblastoma-like variant, ossifying fibroma-like variant, and non-ossifying fibroma-like variant. The small size of this slow growing tumor and the non-specific clinical presentation may present a diagnostic challenge to clinicians. We present a case of a 48-year-old Haitian male who was diagnosed with PMT in the right angle of the mandible. Fewer than 15 cases of PMT presenting in the oral cavity have been reported in the literature. The clinical presentation, the laboratory findings, imaging characteristics, and the histopathologic features for this case are discussed along with the molecular genetic aspects, treatment and prognosis for this rare neoplasm.