Epithelial hyperplasia of the extra-glandular excretory ducts of human minor salivary glands: a histopathologic study.

The histologic features of normal and hyperplastic epithelia of the extra-glandular excretory ducts of human minor salivary glands were studied, and their pathologic significance evaluated. Normal duct epithelium consisted of two layers: inner columnar cells, and basal cubical or squamous cells. A few goblet cells were present among the inner cells. Hyperplasia of the duct epithelia occurred focally or entirely, and was classified into the following histologic types: (1) simple hyperplasia, and (2) metaplastic hyperplasia, which were divided into (a) mucous cell hyperplasia, (b) oncocytic hyperplasia and (c) squamous cell hyperplasia. Squamous cell hyperplasia was subdivided into (i) acanthotic type and (ii) reserve cell-like type with or without dysplasia. Simple or metaplastic epithelial hyperplasia of the extra-glandular excretory ducts of minor salivary glands may be induced by chronic inflammation or other types of irritation, and proliferating cells of such regenerating tissue sometimes exhibit features reminiscent of a neoplastic process. Furthermore, it is suggested that metaplastic epithelial hyperplasia of the excretory minor salivary gland ducts could be the site of origin of tumor development, i.e., some oral squamous cell carcinomas may arise from primary lesions in the hyperplastic epithelium of the extraglandular excretory minor salivary gland ducts.