Fig. 3.

Biopsy cases of colorectal cancers with MMR deficiency but indeterminate MLH1 expression (MSI-H by PCR analysis and loss of MLH1 on subsequent resection specimens). a MLH1/PMS2 MMR-deficient colorectal cancer showing reduced nuclear MLH1 immunostaining with punctate nuclear expression (blue arrows) and preserved, intense, nuclear control in stromal cells (red arrows); b MLH1/PMS2 MMR-deficient colorectal cancer showing relatively weak nuclear expression of MLH1 (blue arrows) which is only slightly reduced compared to preserved, intense, nuclear control in stromal cells (red arrows); c MLH1/PMS2 MMR-deficient colorectal cancer showing relatively weak nuclear expression and nuclear punctate expression of MLH1 (see blue arrows); red arrows show internal control non-neoplastic crypts with preserved intense nuclear expression. Scale bar—50 µm, magnification ×40