IMMUNOHISTOCHEMICAL EXPRESSION OF THYMIDYLATE SYNTHASE IN DIFFERENT GRADES OF COLORECTAL CARCINOMA

Objective: To Evaluate the Immunohistochemical Expression of Thymidylate Synthase in different grades and histological types of Colorectal Carcinoma. Study Design: Cross sectional, Descriptive study Place and duration of study: This study was conducted from June 2019 to November 2020 in the Department of Pathology at Postgraduate Medical Institute Lahore / Lahore General Hospital.                                                                                            Methodology: Forty resected gut specimens diagnosed on light microscopy as Colorectal adenocarcinoma were included on the basis of non-probability, consecutive sampling technique. Cases were reviewed and histological typing and grading was done separately by two competent Histopathologists. Immunohistochemical staining for Thymidylate Synthase was performed. Results of Thymidylate Synthase immunostaining were interpreted by the two observers based on the cytoplasmic staining of tumor cells. Thymidylate Synthase expression was quantified through a visual grading system depending upon the staining intensity and percentage of stained cells.                                                                             Results:  Out of 40 cases of adenocarcinoma, majority of the patients (45%) belong to the age range of 51-60 years. There were 31(77.5%) male patients while 9(22.5%) were females. 28 (22%) cases were classified as low grade while 12 (11%) cases were reported as high-grade carcinomas. Amongst these Thymidylate Synthase expression was seen in 78.6% of low-grade carcinoma and 91.6% of high-grade carcinomas. Regarding histological subtyping, 23(57.5 %) cases were identified as non-mucinous adenocarcinomas, (9)22.5% as mucinous adenocarcinoma and (8) 20% as signet ring adenocarcinoma. Thymidylate Synthase expression was found to be similar i.e., 78% in non- mucinous as well as mucinous carcinomas however, 100% positivity was noticed in signet ring carcinomas. The overall positivity for Thymidylate Synthase was found to be 82.5%.                                                Conclusion: Colorectal carcinoma was prevalent among males of 51-60 years of age. 82.5% cases of colorectal carcinoma expressed Thymidylate synthase receptors and its expression was found to be higher in high grade tumors.