36th European Congress of Pathology – Abstracts

Background & objectives: The study analysed KRAS, NRAS and BRAF status as well as mismatch repair (MMR) protein expression and microsatellite instability (MSI) in synchronous sporadic colorectal carcinomas (sCRC) to assess genomic alterations among lesions in the same patient. Methods: Sixteen patients (13 males, 3 females) with sCRC were studied. Fourteen patients present two sCRC, while two had three. Tumour samples were formalin-fixed, paraffin-embebbed, processed for DNA extraction and analysed for mutations in KRAS, NRAS, and BRAF as well as for MSI analysis using qPCR. Immunohistochemistry was performed to evaluate the expression of MSH2, MSH6, MLH1, and PMS2 proteins. Results: Of 34 samples, 19 (55.9%) had KRAS mutations; discordant KRAS status was found in 8 (50%) of 16 sCRC patients. NRAS mutation in codon 61 was found in 1 (2.9%) sample and a discordant NRAS status was observed only in this patient. BRAF mutation in codon 600 was found in 3 (8.8%) samples from the same patient; concordant BRAF status was observed in all patients. Notably, the patient harboring the BRAF mutation displayed dMMR/MSI status in all lesions; concordant MMR/MSI status was observed in all patients. Conclusion: A discordance of genomic alterations has been documented in 9 (56.25%) of 16 patients. Therefore, molecular characterization should be assessed on each lesion to better define disease management of sCRC patients.