A new histochemical technique of use in the interpretation and diagnosis of adenocarcinoma and villous lesions in the large intestine.

The periodic acid-thionin Schiff/potassium hydroxide/periodic acid-Schiff (PAT/KOH/PAS) procedure has been used to investigate the histochemical staining characteristics of the mucins found in adenocarcinoma and villous lesions of the large intestine. The 46 blocks examined represented 58 lesions from 37 patients, all of whom had had resections for carcinoma of the colon. tin sharp contrast to normal colon, none of the adenocarcinomas stained red with the PAT/KOH/PAS. With two exceptions the poorly and moderately differentiated adenocarcinomas stained blue, whereas of the well differentiated lesions half were blue and half purple. The malignant villous lesions demonstrated the same trends, although a larger percentage were purple. None of the benign lesions stained blue. It is suggested that malignancy in the colon is accompanied by an increase in blue staining in the PAT/KOH/PAS technique and that such staining may be of value in the interpretation of highly atypical adenoma where it might identify the onset of malignancy. This change in staining indicates a distinct alteration in the chemistry of the mucins which we interpret as a reduction in the degree of side chain O-acylation of their constituent sialic acids.