Subepithelial Fibrinous Accumulation and Associated Epithelial Proliferation in Laryngeal Nodules

Abstract

Objective: Fibrinoid accumulation in the larynx and increase in the subepithelial collage- nous connective tissue result in overgrowth. Mucosal epithelium may proliferate downward to organize and remove the fibrinoid accumulation. This downward proliferation may cause an invasive cancer-like image. This study focused on the pathogenesis of the accumulation of fibrinoid substance and the development mechanism of the associated squamous epithelium proliferation. Methods: Five hundred and seventy-five laryngeal nodules were reexamined and 111 of them with varying degrees of irregular downward squamous epithelial proliferation were included in the study. Immunohistochemical staining of CK5/6, CK17, CK14, collagen type I, collagen type III, collagen type IV, and fibrinogen was performed. A modified Masson’s trichrome method was used for the histochemical staining of collagen. Results: Edema was present in 18% of the acute lesions and fibrin deposition in 42%. Rela- tively mature lesions mostly contain dense collagen fibers. The intensity of collagen type III was inversely proportional to the amount of fibrin accumulation. Collagen type IV was found in the epithelial and vascular basement membranes. A decrease in fibrin staining intensity and the presence of collagen type I and type III indicated the replacement of fibrin with col- lagen. Basal-type keratins showed more pronounced staining in the regenerated areas of the epithelium. As the laryngeal subepithelial fibrinoid accumulation was replaced with collagen, regression of the lesion became difficult. Conclusion: Irregular squamous epithelial proliferation occurs independent of the stage of the lesion. Although the etiology is different, the resulting lesions are histologically similar to those seen in the ligneous mucosal disease