Sinonasal Phosphaturic Mesenchymal Tumor: A Rare and Misinterpreted Entity

Abstract

Objectives Oncogenic osteomalacia is a paraneoplastic syndrome in which the tumor secretes a peptide-like hormone, fibroblast growth factor, resulting in urinary loss of phosphates. Methods We present the case of a 50-year-old woman with a benign phosphaturic mesenchymal tumor (PMT) involving the ethmoid sinus with obstruction of the ostiomeatal complex causing unilateral nasal airway obstruction. Results The tumor was initially thought to be an esthesioneuroblastoma based on primary pathology interpretation and on clinical and radiographic appearance. However, a benign PMT was later confirmed by further testing. Conclusion The tumor was removed entirely by the endoscopic transnasal approach, leading to a full resolution of symptoms.

Keywords: endoscopic sinus surgery; phosphaturic mesenchymal tumor; skull base resection.

Fig. 1

(A) Axial and coronal magnetic resonance and (B) computed tomography images depicting the level of involvement within the right nasal and paranasal sinus cavities along with associated mass effect upon adjacent bony structures closely resembling an early stage esthesioneuroblastoma.

Fig. 2

Tumor histology revealing dense cellularity with hemangiopericytoma-like vessels (A), round to ovoid nuclei with a single mitosis (arrow), mild pleomorphism, granular chromatin, and inconspicuous nucleoli in a fibrillary stroma (B), and proliferation marker Ki-67 labeling ∼ 10% of tumor nuclei (C) (H&E stain: A, ×10; B, ×40; and Ki-67 immunoperoxidase stain C, ×20).

Fig. 3

Endoscopic intraoperative views of the tumor involving the nasal cavity (above) and closely associated with the middle turbinate both along the medial and lateral aspects (below).