A mucinous histochemical study on malignancy of aberrant crypt foci (ACF) in rat colon.

The relationship between malignancy and number of crypts (crypt multiplicity) comprising aberrant crypt foci (ACF) was investigated, by studying changes in the mucous nature of ACF with 5 crypts or less, ACF with 6-13 crypts, adenomas and invasive adenocarcinomas induced by 1,2-dimethylhydrazine in distal colon of rats. A paradoxical Con A-staining was performed for goblet cell mucins. Of the sulfomucin-dominant ACF with 1-3 crypts, 82.6% had labile class III mucin, similar to the distal colon in the normal rats. However, in most of the goblet cell mucin produced by the ACF with 4-5 crypts with an indicated relation to colorectal carcinoma or the sialomucin (SiM) -dominant ACF with 1-3 crypts, mucin types other than class I were rarely present. The incidence of class I mucin decreased with the increase in crypt multiplicity of ACF or in the degree of histological malignancy, with the lowest incidence of 40% in adenocarcinomas. In contrast, the incidence of class II mucin increased markedly with the increase in crypt multiplicity of ACF or in the degree of histological malignancy, with the highest incidence in adenocarcinomas (95%). The ACF with 6-13 crypts had a mucous profile similar to that of adenomas. These results suggested that malignancy of ACF related to the crypt multiplicity. In the ACF with 1-3 crypts, SiM-dominant ACF had the potential to progress to malignant lesions.