Chemical and histochemical studies of normal and diseased human gastrointestinal tract. III. Changes in the histochemical and chemical properties of the epithelial glycoproteins in the mucosa close to colonic tumours.

Histochemical, chemical and histological studies were performed on 26 specimens of human colonic tumours and 62 specimens of mucosa taken at distances of 0.5-5.0 cm from the tumour. The tumour glycoproteins were divided almost equally between three anionic types, sulphomucin, sialomucin and mixed sialomucin and sulphomucin. All showed a reduction in staining for side chain O-acylated sialic acid. In 56% of the tumours, this was accompanied by loss of glycoprotein while, in 44%, abundant mucin was still present. Histochemical examination of the mucosal specimens indicated that in 24.2% the side chain O-acylated sialic acids did not differ from normal. In 41.9% there was a focal change and in 33.9% there was a generalized field reduction in the proportion of side chain O-acyl sialic acids. The latter were subdivided into moderate and severe. Chemical analyses correlated well with the histochemical classification of the mucosal specimens and showed that, on average, the classifications focal and severe field change were not due to sampling error. Forty-five per cent of the cases showed only focal change and 40% only field change. Mucosal specimens associated with 60% of the moderately differentiated tumours showed only focal change while those associated with 75% of well-differentiated tumours showed only field change. Abnormal patterns of staining for side chain O-acylated sialic acids (a) were largely independent of the distance from the tumour, (b) occurred in the presence of a normal pattern of staining for sialomucins and sulphomucins and (c) were associated with 61.4% of the specimens that showed no discernible evidence of histological abnormality. In contrast, only one specimen showed evidence of histological change without a corresponding change in O-acylated sialic acids. The data suggest that abnormal patterns of staining for O-acylated sialic acids may represent premalignant change but their precise significance and specificity requires further studies of non-neoplastic diseases of the colon.