Histogenesis of microscopic adenoma and hyperplastic (metaplastic) gland in nonpolyposis coli.

Histogenesis of microscopic adenoma in nonpolypoid colons (those not included in the special disease group of familial polyposis coli) was investigated using complete serial sections with the following results: Adenoma arises from basal cells in the deep layer of the mucosa; and two types of basal cells found were 1) those which had already undergone changes to adenoma and 2) those which are in their transitional stage to adenomas. Early-phase growth of adenoma is brought about by branching. Individual hyperplastic (metaplastic) glands constituting so-called hyperplastic (metaplastic) polyps are considered to be only an expression of one variant in the growing process of adenomas and the glands showing these changes most characteristically have a serrated pattern. Based on these findings, the histogenesis of adenoma in nonpolypoid colons is shown schematically.