From Libre Pathology
COLON, RESECTION: - ADENOCARCINOMA. - TUMOUR HAS BEEN EXAMINED FOR THE MISMATCH REPAIR GENE PRODUCTS. MLH1: ABNORMAL, FOCAL MINIMAL STAINING IN THE TUMOUR COMPARED TO BENIGN BACKGROUND CELLS. MSH2: NORMAL NUCLEAR STAINING. MSH6: NORMAL NUCLEAR STAINING. PMS2: ABNORMAL, ABSENT NUCLEAR STAINING, SEE COMMENT. COMMENT: Abnormal immunohistochemical staining is highly correlated (>99%) with tumours that show high-frequency microsatellite instability (MSI-H) and this tumour should be consider to have microsatellite instability (MSI-H). The MLH1 staining is abnormal; it is very week and focal in the lesion, when compared to the background tissues. PMS2 is completely absent. The expression of PMS2 is lost in tumours with abnormal MLH1 expression. As the MLH1 is decreased but not completely absent, this individual's PMS2 status cannot be determined by immunohistochemistry, and the individual could be considered for furthe investigation of MLH1 status. Abnormal MLH1 expression can be seen in sporadic tumours (associated with MLH1 hypermethylation) as well as in association with Lynch syndrome (LS), also known as hereditary non-polyposis colon cancer (HNPCC). Features associated with LS include young age of onset, strong family history of cancer (especially endometrial, urothelial, other gastrointestinal), and multiple primary LS cancers in one individual. If this patient has these characteristics suggestive of LS, a referral to a genetic counsellor is suggested.