Cawkwell and colleagues, in this issue (see page 409), describe an immunohistochemical method which enables the status of a colorectal carcinoma with respect to the two mismatch repair (MMR) genes, hMLH1 and hMSH2, to be ascertained from paraffin wax sections produced by any diagnostic histopathology laboratory.

Despite many advances in the pathological management of colorectal cancer since Dukes and Bussey1—for example, taking account of the number of lymph nodes containing metastatic tumour or the nature of the infiltrating margin of the tumour,2staging systems have not hitherto provided precise information about the biology and likely behaviour of the tumour in individual cases. By adopting the relatively simple methodology proposed by Cawkwell and colleagues, it should now be possible to assign patients reliably to one of the two main specific categories of MMR status, thereby …