Glomangiopericytoma with CTNNB1 mutation.

Glomangiopericytoma (GPC) is a rare tumour, accounting <0.5% of all nasal cavity tumours. It is classified as borderline malignant to indolent and is associated with perivascular myeloid cells. We report a case of GPC in a woman in her 80s who presented with nasal obstruction. The tumour originated from the nasal septum and was resected via endoscopic sinus surgery. Histopathological examination revealed dense spindle-shaped to oval-shaped mesenchymal cells forming tumour nodules with staghorn-like vessel formation. Immunohistochemical analysis revealed that the tumour cells were positive for α-smooth muscle actin, CD34, β-catenin and cyclin D1, whereas they were negative for STAT6. The percentage of Ki-67-positive cells was approximately 2%. Recent studies have demonstrated a high frequency of β-catenin (CTNNB1) mutations in GPC. We report a case of GPC where identifying CTNNB1 mutations (c.94G>C, p.D32H) was crucial for establishing a definitive diagnosis.