Phosphaturic Mesenchymal Tumor Along the Hallux side Inducing a Chronic non-Healing Wound: A Case Report with Literature Review

Abstract

Phosphaturic mesenchymal tumor (PMT) is a rare paraneoplastic syndrome characterized by renal phosphate wasting, hypophosphatemia, and bone calcification disorders. Complete surgical resection of the tumor is believed to be the most effective treatment measure. However, the diagnosis of PMT is very difficult because of its insidious and small size, especially, when it appears in subcutaneous tissue with a chronic non-healing wound. We report a rare case of a 38-year-old man with a chronic non-healing wound on the left hallux for approximately eight months. Plain radiographic images and magnetic resonance imaging (MRI) revealed a cystic radiolucent shadow in the left distal phalanx. Bone scan observations also showed increased uptake in the same location. Histologically, this tumor was composed of numerous spindle cells with clusters of giant cells. The serum FGF23 level was significantly higher before surgery, with higher FGF23 levels closer to the tumor. Reverse transcription polymerase chain reaction and immunohistochemistry further confirmed the high expression of FGF23 in tumors. These data suggest that FGF23 may be a potential causative factor of PMT. The serum FGF23 levels might be useful for the diagnosis of PMT and localization of the tumor. The tumor was CD56- and D2 to 40-positive and CD31-negative. The non-healing wound caused by PMT might be attributed to the invasive growth of the tumor, destruction of intercellular junctions, and decrease in the number of endothelial cells.