Immunohistochemical Expression of Thymidylate Synthase in Different Pathological Stages of Colorectal Carcinoma

Objective: To evaluate thymidylate synthase (TS) immunohistochemical expression across various colorectal cancer (CRC) stages in a Pakistani population. Methodology: A cross-sectional analytical study was conducted from June 2019 to November 2020, including 40 histologically diagnosed colorectal adenocarcinoma cases. Clinical data were collected, and specimens were processed and staged according to the TNM staging system. TS expression was evaluated based on cytoplasmic staining intensity and percentage of stained cells. Statistical analysis was performed using SPSS version 20. Results: The majority of cases were male (77.5%) aged 40 to 70, with predominant T3-stage tumors (52.5%). TS positivity was observed in 82.5% of cases but did not significantly correlate with demographic or clinicopathological factors. The higher sensitivity of TS was noted in the T1 and T4 stages. Conclusion: Thymidylate synthase (TS) expression was detected in the majority of Colorectal cancer cases, with particularly notable sensitivity in T4 tumors and potential utility as a biomarker in early (T1) and advanced (T4) stages. However, TS expression did not demonstrate significant associations with demographic or clinicopathological factors, such as age, gender, or tumor characteristics. These findings underscore the need for further research with large cohorts and a refined scoring system to elucidate TS's prognostic and therapeutic implications, particularly in its role as a staging biomarker. Key Words: Colorectal cancer, Thymidylate synthase, Immunohistochemistry, Clinicopathological factors, Staging biomarker.