β1 and β4 integrin expression in methacarn and formalin‐fixed material from in situ ductal carcinoma of the breast

The integrins are αβ heterodimeric transmembrane proteins mediating cell‐substratum as well as cell‐cell interactions. Previous distribution studies on integrin expression have been limited by the requirement for cryostat sectioned tissues, and consequent poor resolution. We have examined 40 examples of ductal carcinoma in situ (DCIS) for the expression of both β1 and β4 integrin chains. These showed strong polarized membrane staining of residual myoepithelial cells (correlating with expression of smooth muscle specific actin) and of the basement membrane region with β1 and β4 antibodies respectively. In 12 out of 40 cases, the DCIS was negative for the β1 chain and a variable pattern of reactivity was seen in the remaining cases. The β4 chain was detected focally and weakly in the tumour cells of 7/40 DCIS and strongly in one; all of these cases were also positive for the β1 chain. Of the 22 cases where co‐existent invasion was present, the infiltrating component showed either a similar degree or a diminution of the extent of immunostaining when compared with the in situ component; only one showed enhanced staining (β1 only). This study demonstrates that two of the main β chains, β1 and β4, can be effectively demonstrated on methacarn and cold (4°C) formalin‐fixed tissues by avidin‐biotin indirect immunoperoxidase staining and that the results are similar to those achieved using frozen tissue.