Results: Of 321 CRCs, (13/123 early-onset vs. 21/198 late-onset) were detected to be dMMR. Nine early-onset cases and 14 late-onset ones, with a loss of MLH1 underwent testing for the BRAF mutation, none of the early-onset and four late-onset were recognized as positive BRAF mutation. MajorityThe majority of the positive LS tumors from early-onset patients had arisen in the distal part (8/11 vs. 8/14), all of which were occurred in the rectum or sigmoid.

Conclusion: Clinically, these findings suggest that in case of limitation for BRAF testing, the practitioner in Iran may consider managing early-onset dMMR cases like LS until access to BRAF testing becomes available to them, before germline testing to accurately diagnose LS.

A genetically inherited autosomal disorder that increases the risk of many types of cancer is known as

Lynch Syndrome (LS), whichand is often called hereditary nonpolyposis colorectal carcinoma (HNPCC). This disorder is diagnosed due towith molecular testing in patients with mutations in one of the four mismatch repair (MMR) genes, including MLH1, PMS2, MSH6 and MSH2 1. Individuals with LS have a lifetime risk of approximately for colorectal carcinoma (CRC) 2. Moreover, these patients are at the high risk of endometrial, ovarian, and brain extra-colonic cancers 1.