Investigation of Keratinized Squamous Epithelium from Mastoid Cortical Bone Dust in Patients with or without Cholesteatoma.

Objective: This study aimed to investigate squamous metaplasia in mastoid cells of patients undergoing surgery for chronic otitis media (COM) with or without cholesteatoma. Bone dust was stained with hematoxylin and eosin (H&E) for squamous cells and keratin and immunohistochemically for p63. Additionally, the feasibility of routine pathological examination of bone dust via H&E staining was evaluated for cost-effectiveness and for identifying patient groups needing advanced follow-up. Methods: Thirty-one patients with COM were enrolled: 14 with cholesteatoma (study group) and 17 without cholesteatoma (control group). Mastoid bone dust obtained during surgery was examined specifically for the presence of squamous cells, keratin, and p63, with evaluation performed using H&E and immunohistochemical staining techniques. Findings were compared between the study and control groups. Results: Keratin was significantly more frequent in the study group than in controls (43% vs. 6%, p=0.01). No significant differences were observed for squamous cell (p=0.43) or p63 expression (p=0.20). However, when any of the three markers were positive, a statistically significant difference was found between the groups (43% vs. 12%, p=0.049). Conclusion: These findings suggest that the mastoid air cell systems of patients with cholesteatoma may be affected differently prior to cholesteatoma spreading to the mastoid system. This could be linked to microcirculation of inflammatory proteins, impaired aeration, and the formation of retraction pouches. These results align with the metaplasia theory as a possible explanation for the etiopathogenesis of acquired cholesteatoma.