The Klintrup–Mäkinen Score as a Simple H&E-Based Indicator of CD8+ T-Cell Infiltration and Nodal Status in Colorectal Adenocarcinoma

The interaction between tumor cells and the host immune response plays a key role in the advancement of colorectal adenocarcinoma. The Klintrup–Mäkinen (KM) score represents a simple and efficient histological method for evaluating the inflammatory reaction at the invasive tumor front, but its relationship with specific T-cell populations remains incompletely defined. This study aimed to investigate the association between the KM score and T-cell infiltration, assessed by CD3, CD4, and CD8 immunohistochemical markers, as well as its correlation with clinicopathological parameters. A total of 150 patients diagnosed with colorectal adenocarcinoma between 2022 and 2025 were included. Cases were stratified into low KM (scores 0–1) and high KM (scores 2–3) groups. Immunohistochemical staining for CD3, CD4, and CD8 was performed and evaluated at the invasive front. Associations between KM score, immunohistochemical markers, and clinicopathological variables were analyzed using the chi-square or Fisher’s exact test, while age was assessed using the Mann–Whitney U test. High KM scores were significantly associated with increased expression of CD3 (p < 0.001), CD4 (p = 0.032), and particularly CD8 (p < 0.001). Low KM scores were more frequently associated with lymph node metastasis (p < 0.001) and poor tumor differentiation (p = 0.010). No significant differences were observed in relation to age, gender, pT stage, lymphovascular invasion, perineural invasion, tumor budding, necrosis, or distant metastasis. CD8 expression was significantly associated with lymph node status (p = 0.021), but not with other markers of tumor aggressiveness. The KM score correlates with the density of T lymphocytes at the invasive front, particularly CD8-positive cells, and is associated with relevant pathological features such as lymph node metastasis and tumor differentiation. These findings support its role as a simple histological indicator of the tumor immune microenvironment in colorectal adenocarcinoma.