Peanut lectin-binding sites and mucins in benign and malignant colorectal tissues associated with schistomatosis.

An immunohistochemical and histochemical comparative study was carried out in benign and malignant colorectal tissues with and without schistosomiasis. This included a quantitative determination of peanut lectin (PNA)-binding sites and proliferating cell nuclear antigen (PCNA) expression and histochemical detection of mucin changes. 133 cases were studied, including 70 cases of colorectal carcinoma associated with schistosomiasis (CCS) and 63 cases of colorectal carcinoma without schistosomiasis (CC). Significant differences were found in the type of mucin-containing carcinomas (MC) between CCS and CC. 65% of non-tumorous mucosa adjacent to MC of the CCS group expressed PNA-binding sites, significantly higher than those of the MC in the CC group (31%). The non-tumorous mucosa in cases of MC of the CCS group also showed a high percentage of sialomucin-predominant secretion (69%, vs 38% in MC of the CC group). Consistently, the presence of PNA-binding sites in MC tumors of the CCS group was increased, compared with that in the same subtype in the CC group (respectively 65% and 31% of strong positivity for PNA). However, no differences in expression of PNA and mucin changes were demonstrated in the surrounding mucosa and tumorous tissues of non-mucin-containing carcinomas (NMC) between CCS and CC. The expression of PCNA was not different between CCS and CC and their subtypes. Our findings suggest a close relationship between mucin-containing colorectal carcinomas and schistosomiasis japonica.