Clinical, Immunohistochemical, and Inflammatory Profiles in Colorectal Cancer: The Impact of MMR Deficiency

Background/Objectives: Mismatch repair (MMR) deficiency assessment has proven to be a valuable tool for prognostic evaluation and therapeutic management guidance in patients with colorectal cancer (CRC). Our study aimed to investigate the associations between MMR deficiency and a range of clinicopathological parameters. Methods: We conducted a retrospective observational study including 264 patients diagnosed with CRC, for whom immunohistochemical (IHC) data were available. Statistical analysis was performed using the Python 3.12.7 programming language within the Jupyter Notebook environment (Anaconda distribution). Results: MMR deficiency was identified in 18.18% of patients. It was significantly associated with younger age (<50 years), female sex, right-sided tumor location, poor tumor differentiation (G3), smoking, and loss of CDX2 expression (p < 0.001). MLH1 and PMS2 were the most frequently affected proteins, with concurrent loss in 77.08% of MMR-deficient cases. Loss of MLH1 expression correlated with female sex (p = 0.004), right-sided location (p < 0.001), poor differentiation (p < 0.001), and loss of CDX2 expression (p < 0.001). Additionally, the loss of PMS2 expression was associated with female sex (p = 0.015), right-sided tumor location (p = 0.003), and poor differentiation (p < 0.001). No significant associations were identified between MMR status and tumor stage, histological subtype, PLR, or NLR values. Conclusions: Gaining deeper insights into the clinical relevance of MMR status in CRC could contribute to improved testing rates and support the design of tailored management strategies that address the specific biological features of these tumors.