Sinonasal Phosphaturic Mesenchymal Tumor: A Case Report.

Phosphaturic mesenchymal tumor (PMT) is a rare mesenchymal neoplasia usually located in the soft tissue and the bone. It is seen in older ages and is most commonly localized in the extremities. Here, we present a rare case of PMT located in the sinonasal region. A 56-year-old male patient was admitted with complaints of congestion in the right nasal cavity and limitation of upward gaze in the right eye. Computed tomography revealed a contrast-enhancing mass with heterogeneous density obliterating the bilateral frontal sinus, the frontoethmoidal recess, the right osteomeatal complex and the right sphenoid sinus, extending to the superior extraconal area in the right orbit. Since the tumor type cannot be determined precisely in the pathological evaluation of incisional biopsy, an excisional biopsy was performed with the preliminary diagnosis of malignancy. But histopathological examination revealed a PMT. PMT is a highly uncommon neoplasm that remains largely unfamiliar to clinicians, surgeons, and pathologists, particularly when arising in rare locations like the sinonasal region. Its histomorphological characteristics can overlap with various other entities, necessitating a broad differential diagnosis.