Histological and immunohistochemical study of pars tensa retraction pocket.

OBJECTIVE

To study the histological and proliferation characteristics of the pars tensa retraction pocket. To investigate the hypothesis that such retraction pockets may demonstrate breaks in the epithelial basement membrane.

STUDY DESIGN

Prospective evaluation. Fifty stage II-IV surgically resected retraction pockets.

SETTING

Tertiary care academic hospital.

METHODS

Paraffin sections stained with hematoxylin and eosin. Basement membrane evaluation by Periodic acid-Schiff (PAS) and silver-methenamine (SM). Evaluation of cellular proliferation by immunohistochemistry (MIB-1 score).

RESULTS

Following are findings noted as frequent but not invariable in pars tensa retraction pockets: (1) subepithelial chronic inflammation (86%), (2) proliferation and hyperkeratinization of the outer epithelial layer, (3) epithelial cones with proliferating cells (increased MIB-1 score) in the basal epithelial layer (39%), (4) loss of the middle double collagen layer (71%), and (5) loss of the inner mucosal layer (33%). Inflammation and cellular proliferation were noted as ubiquitous among all grades. A trend was noted along progressive grades of retraction (II-IV) for an increasing incidence of basal epithelial cones, middle collagen layer loss, and inner mucosal layer loss. Focal loss of basement membrane was noted in several cases with PAS staining, but further staining with the SM in all such cases indicated the basement membrane to be intact.

CONCLUSION

A continuum of progressive histological features akin to cholesteatoma is noted with increasing grades of retraction (II-IV). Breach of the basement membrane was recently reported as a feature of cholesteatoma but is not a feature of retraction. The near universal presence of inflammation as noted suggests an etiological role.