Sinonasal and skull base phosphaturic mesenchymal tumours: a case series and narrative review

Phosphaturic mesenchymal tumours (PMTs), which are common causes of tumour-induced osteomalacia (TIO), are exceptionally uncommon in the sinonasal tract and skull base. PMTs are characterized by their nonspecific location, small size, and indolent growth. When they occur in the sinonasal region and skull base, they often lack typical sinonasal symptoms, which poses significant diagnostic challenges and contributes to high rates of missed and misdiagnosis. A retrospective analysis was conducted on 5 patients with pathologically confirmed sinonasal/skull base PMTs treated at our institution from December 2015 to March 2025. The study cohort comprised three male and two female patients aged 28 to 67 years. The sites of involvement were the left sinonasal cavity (n = 3), right sinonasal cavity (n = 1), and sinonasal skull base (n = 1), with all patients undergoing surgical resection of the lesions. Our findings indicate that the increased incidence of missed and misdiagnoses primarily arises from tumour obscurity, atypical clinical manifestations, and insufficient clinical recognition of the condition. Persistent hypophosphataemia provides vital diagnostic information. PET demonstrating somatostatin receptor positivity and immunohistochemistry revealing SSTR2+/SATB2+ expression are key auxiliary diagnostic tools. Monitoring postoperative serum phosphorus levels can aid in the effective evaluation of cure and recurrence.