Distinct histopathologic features of radiation‐induced chronic sinusitis

Background Chronic rhinosinusitis (CRS) is a commonly observed sequela after radiation therapy to the paranasal sinuses. The histopathologic features of radiation‐induced CRS have yet to be determined and may have major implications in disease management. Methods A structured histopathology report was utilized to analyze sinus tissue removed during functional endoscopic sinus surgery (FESS). Histopathology variables, Lund‐Mackay score (LMS), and 22‐item Sino‐Nasal Outcome Test (SNOT‐22) scores were compared among patients with radiation‐induced CRS (CRSr), CRS without nasal polyps (CRSsNP), and CRS with nasal polyps (CRSwNP). Results Fifteen CRSr, 43 CRSsNP, and 56 CRSwNP patients who underwent FESS were analyzed. Compared with CRSsNP, CRSr cases had increased squamous metaplasia (40.0% vs 9.3%, p < 0.013) and subepithelial edema (53.3% vs. 2.3%, p < 0.001). Compared with CRSwNP, CRSr cases had fewer eosinophils per high‐power field (20.0% vs 50.0%, p < 0.034), less basement membrane thickening (33.3% vs 76.8%, p < 0.002), and fewer eosinophil aggregates (0.0% vs 30.4%, p < 0.009). CRSr had significantly greater mean LMS (13.47 ± 5.13 vs 7.07 ± 4.79, p < 0.001) compared with CRSsNP. Conclusion Radiation‐induced CRS patients exhibited greater squamous metaplasia and subepithelial edema when compared with a cohort of patients with CRSsNP, and decreased eosinophilia and basement membrane thickening compared with a cohort of CRSwNP patients. CRSr cases demonstrated no difference in eosinophilia or neutrophilia compared with CRSsNP, and decreased eosinophilia compared with CRSwNP, lending further credence to the unique nature of radiation in the development of CRS in this patient group. These findings may have major implications with regard to extent of surgical intervention and medical management.