Phosphaturic mesenchymal tumor of the nasal cavity and paranasal sinuses: A clinical curiosity presenting a diagnostic challenge.

Phosphaturic mesenchymal tumor (PMT) is a rare mesenchymal neoplasm associated with tumor-induced osteomalacia (TIO) and elevated serum FGF-23. Common in extremities, PMT rarely occurs in sinonasal region. We report a series of sinonasal PMT diagnosed at our institute over a 6-year period. Six cases of sinonasal PMT were identified during this period, of which five presented with features of TIO. Median age of patients was 45.5 years. All six tumors were composed of stellate to spindled cells, with prominent staghorn vasculature in four cases. Typical smudgy matrix was seen in all cases, but only focally; grungy calcification was absent. Accurate diagnosis of PMTs is imperative, as complete excision leads to dramatic resolution of TIO symptoms. Lack of knowledge of this entity prevents clinicians from ordering relevant investigations. Absence of specific morphological features, like grungy calcification, and presentation at atypical locations makes the diagnosis challenging. Awareness of this entity is essential in order to suspect PMT in patients presenting with a soft tissue mass and features of TIO, however unusual the location may be.