Annalice Gandini

Abstract Mismatch repair deficiency (dMMR)/Microsatellite instability (MSI) plays a central role in colorectal cancer (CRC) as a predictive and prognostic biomarker and as a “red flag” for diagnosis of Lynch Syndrome (LS). HER2 is emerging as a therapeutic target and clinical trials are ongoing. Several reports suggested that HER2 amplification could be mutually exclusive with dMMR/MSI, which is mostly associated with HER2 mutations or other alterations.

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A man of 90 years old in good general condition with a past medical history of hypertension, hepatitis A, chronic pancreatitis, and chronic kidney disease (CKD) came to our attention in January 2019, when, due to a prostatic suspicious lesion, he underwent a prostatic biopsy. The histological exam was consistent with a prostatic adenocarcinoma Gleason Score of 5 + 4 = 9/10.