Ultrastructural study of the normal mucosa-adenoma-cancer sequence in the development of familial polyposis coli.

Ultrastructural changes that occurred in the colon epithelia of patients with familial polyposis coli were investigated. Criteria of gradation of the crescendo changes from the mucosa in the controls, through the "normal" mucosa between polyps and adenomas in various stages of dedifferentiation, to invasive carcinoma were established. Our criteria were based on the following requirements: a) vesiculation and increasing numbers of small electron-dense bodies (secretory granules) and lysosomes in the mature and immature absorptive cells, b) presence of immature and undifferiated cells, c) variation in the globlet cells and appearance of atypical secretory cells, and d) nuclear changes. The results illustrated the adenoma-carcinoma sequence and added strong evidence to support its occurrence. Furthermore, this ultrastructural study revealed cellular changes that preceded adenomatous growth and may be of value as markers of early stages of cancer. However, this study also revealed a close link between the function and morphology of the mucosal epithelium.