Phosphaturic mesenchymal tumor: Case report.

Phosphaturic mesenchymal tumors (PMT) are an extremely rare pathologic phenomenon that presents as paraneoplastic tumor-induced osteomalacia. Their diagnosis is often significantly delayed due to their rare occurrence in addition to the generalized and vague symptoms of their presentation including progressive bone pain, myopathies, arthralgias, fractures, and generalized weakness. This case report identifies a very characteristic presentation of a 37-year old African American male suffering from a PMT; with symptom onset presenting over 5-years prior to presentation with a consistent complaint of progressive and debilitating quadriparesis. The tumor was first identified by pelvic computerized tomography, although it was initially thought to be a noncontributory benign soft tissue mass. It was only after being hospitalized due to a severe and unresponsive hypophosphatemic state (less than 1 mg/dl) that the collective differential switched to one of a PMT with follow up nuclear 99mTc bone scintigraphy and magnetic resonance imaging being used to aid in the overall assessment of changes, extent, and general metabolic properties of the tumor. The confirmatory diagnosis of a PMT was later established through both serum fibroblast growth factor 23 testing and histopathologic review of the surgically removed specimen. By including this rare but curative disease into the differential of osteomalacia and thereby further examining patient serum phosphate levels, the previous 5-7 year delay in diagnosis will be dramatically reduced.