Clinicopathological and Molecular Features of Primary Inflammatory Myofibroblastic Tumor in Nasal Cavity and Paranasal Sinuses.

Background: Inflammatory myofibroblastic tumor (IMT) in the nasal cavity and sinuses is rare and has special clinical and pathological characteristics with poor prognosis. This study aimed to investigate the clinicopathological and molecular features of primary IMT in the nasal cavity and paranasal sinuses.

Methods: The clinical features, histopathological findings, immunohistochemical findings and results of molecular genetic examination were retrospectively analyzed in 25 patients who were diagnosed with IMT in the nasal cavity and paranasal sinuses.

Results: Tumor tissues were mainly composed of obese spindle-shaped myofibroblasts, fibroblasts, and chronic inflammatory cells. The inflammatory cells included plasma cells, lymphocytes, eosinophils, foam histiocytes and multinuclear giant cells. Immunohistochemical staining showed the tumor was positive to anaplastic lymphoma kinase (ALK) in two patients. fusion mutation was detected by PCR in only 1 patient.

Conclusion: Nasal and paranasal sinus IMTs are rare, exhibit histopathological diversity with low specificity, and require careful differentiation from inflammatory and autoimmune disorders. These tumors demonstrate a worse prognosis compared to IMTs in other anatomic locations, along with a significantly lower rate of ALK gene rearrangement. Identifying molecular target alterations can enhance precision diagnosis and targeted therapeutic strategies.