Differentiation‐associated changes in mucin glycoprotein antigenicity in mucosa adjacent to rare gastrointestinal tract tumours of non‐mucosal origin

We have investigated changes in mucin antigenicity and morphology in the perineoplastic mucosa adjacent to rare, predominantly non‐mucosal gastrointestinal (GI) tumours. Twenty‐nine tumours of small and large intestine, including primary mesenchymal and ectodermal tumours, were examined immunohistochemically using 11 monoclonal antibodies (MAbs) raised against SIMA and LIMA (small and large intestinal mucin antigens). Non‐epithelial GI tumours were essentially non‐reactive, while adjacent mucosa showed altered mucin expression and morphology, in particular, features of transitional mucosa (TM). Combinations of different SIMA epitopes were detected adjacent to all colorectal tumours, and, similarly, LIMA epitopes adjacent to small intestinal tumours. Specific patterns adjacent to certain tumours may reflect influences of factors produced by individual tumours on mucin composition. Altered antigenicity and morphology in TM thus appear to be reactive changes in response to a wide range of GI tumours, presumably as a consequence of factors secreted by the tumour and/or a host response to the tumour.