Morphology and histochemistry of the mucosa surrounding small oligotubular adenomas of the large bowel.

The transitional mucosa surrounding adenomas and carcinomas of the large bowel is characterized by a reversion of mucus secretion from sulphomucin to sialomucin and a hyperplasia of crypts and epithelial cells. The specificity of this phenomenon is still a controversial issue. Therefore we studied 72 oligotubular adenomas of the large bowel and the adjacent mucosa by means of histochemistry and morphometry. The peak of sialomucin production is found within the crypts immediately adjacent to the adenoma, whereas the more distant crypts secrete less. The cellular diameter and the depth of the crypts behave in a similar manner, they decrease with increasing distance from the adenoma, still being much higher than in the normal mucosa. The crypt depth correlates well to sialomucin production. The existence of the transitional mucosa around small oligotubular adenomas may indicate, that this mucosal change is not merely secondary to the presence of carcinoma but may be of importance as a precursor lesion of neoplastic changes of the colon and rectum.