Clinical characteristics of patients with colorectal cancer with double somatic mismatch repair mutations compared with Lynch syndrome.

Pearlman R, Haraldsdottir S, de la Chapelle A, Jonasson JG, Liyanarachchi S, Frankel WL, Rafnar T, Stefansson K, Pritchard CC, Hampel H
J Med Genet in press 03/15/2019

Abstract

BACKGROUND: Patients with colorectal cancer (CRC) with mismatch repair-deficient (dMMR) tumours without

METHODS: We included patients with CRC from Ohio 2013-2016 and Iceland 2000-2009. All had microsatellite instability testing and/or immunohistochemistry (IHC) of MMR proteins, and

RESULTS: Of the 232 and 51 patients with non-methylated dMMR tumours in the Ohio and Iceland cohorts, respectively, 57.8% (n=134) and 45.1% (n=23) had LS, 32.8% (n=76) and 31.4% (n=16) had DS PVs, 6% (n=14) and 9.8% (n=5) were unexplained and 4.3% (n=10) and 13.7% (n=7) had incorrect IHC. Age of diagnosis for DS patients was older than patients with LS (p=3.73×10

CONCLUSIONS: Individuals with LS are 15× more likely to meet Amsterdam II criteria and >5× more likely to have multiple cancers as compared with those with DS tumours. Furthermore, isolated loss of MSH6 or PMS2 protein predicts LS.

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