Clinicopathological features of colon cancer depending on the dMMR status of the tumor

Aim. To conduct a clinical and morphological assessment of the characteristics of colon cancer depending on the dMMR / pMMR status of the tumor. Materials and methods. A retrospective study included 66 patients with operable colorectal cancer (CRC) (T 1-4bN 0-2bM 1), who were treated at Cancer Research Institute of Tomsk National Research Medical Center (NRMC). The average age of the patients was 64.4 +/- 12.8 years. All patients underwent hemicolectomy or colon resection, as well as intraoperative resection of distant metastases, if present. Results. We determined that in CRC patients with pMMR tumors, hematogenous metastases were detected in 27.3% of cases, while in patients with dMMR tumors, hematogenous metastases were detected only in 6.1% of cases (p = 0.021). A comparative analysis of dMMR and pMMR tumors also allowed to establish higher frequency of perineural invasion among the pMMR subgroup of carcinomas (p = 0.039). The sign of tumor budding was found both in dMMR carcinomas (36%) and in pMMR tumors (45%). This sign was associated with damage to regional lymph nodes (p = 0.0017). A more detailed analysis of the tumor budding phenomenon showed that in dMMR tumors, Bd1 low-grade budding (83%) predominated. In pMMR tumors, Bd2 intermediate-grade budding (33%) and Bd3 high-grade budding (26.7%) prevailed. Bd2 and Bd3 tumor budding types were associated with hematogenous metastasis (p < 0.001). Conclusion. The obtained data demonstrate the differences in such pathomorphological parameters as perineural invasion and the degree of tumor budding depending on the dMMR / pMMR status of the tumor. These histologic parameters in tumor tissue are also associated with higher incidence of distant metastasis in patients with pMMR carcinomas as opposed to patients with dMMR tumors.