Immunohistochemical Expression (IHC) and Fluorescence In Situ Hybridization (FISH) of EGFR in Colorectal Carcinoma

Adenocarcinoma of the colon is the most common malignancy of the gastrointestinal tract and is a major cause of morbidity and mortality worldwide. Epidermal growth factor receptor (EGFR) is also known as HER-1 or erb-B1. The beginning of EGF to EGFR produces a biological signal to the cell that initiates several functions that promote tumor growth, including cell invasion and metastasis, repair and new blood vessel formation. Thus, EGFR is recognized as an important player in colorectal cancer (CRC) initiation and progression. In this study, total 61 cases of colorectal carcinoma were included and histological grading, immuno-histochemical (IHC) expression and fluorescence in situ hybridization of EGFR were conducted. For the grading, 11/61(18%) cases were well differentiated, 38/61(62%) cases were moderately differentiated and 12/61(20%) were poorly differentiated colorectal carcinoma. EGFR IHC immune expression was positive in 50/61(82%) cases and negative in 11/61(18%) cases. All 11 cases of well differentiated cases gave EGFR IHC positive immunoreaction. Among the 38 cases of moderately differentiated adenocarcinoma, 30 cases showed EGFR IHC positivity and 8 cases gave no reaction. Nine out of 12 cases of poorly differentiated adenocarcinoma showed EGFR IHC positive and 3 cases gave no reaction. Half (10/20, 50%) of the EGFR IHC highly positive cases showed FISH positive and other half cases give FISH negative reaction. Detection of EGFR is mainly for anti-EGFR targeted therapy. Therefore, this study aids in selection of patients for anti-EGFR targeted therapy and helpful in treatment options and disease management. Moreover, EGFR FISH can be tested together with KRAS mutation and can predict the treatment response and the disease outcome.