Breast Carcinoma – A Comparative Study of Immunohistochemistry and Fluorescence in Situ Hybridization for Her-2 Assessment and Association of ER, PR, HER-2 and Ki-67 Expression with Clinico-Pathological Parameters

BACKGROUND & OBJECTIVE: Breast cancer is the most common cancer in developed and developing countries. This study mainly addresses the issue of an equivocal result in IHC, which then needs further assessment if the patient has to receive targeted therapy. The study aimed to detect the expression of Her2/neu protein in breast cancer by immunohistochemistry (IHC) and Fluorescence in situ Hybridization (FISH) and evaluate concordance and discordance between the two methods. Also, the clinicopathological parameters in these patients were studied in association with ER, PR, HER-2, and Ki-67. METHODS: This study was conducted on 34 female carcinoma breast specimens, including core biopsies and mastectomies. Each case underwent histopathological and immunohistochemical studies for (Estrogen Receptor) ER, (Progesterone Receptor) PR, (Human Epidermal growth factor Receptor 2) HER-2, and Ki-67. In addition, FISH was done on all the samples to detect Her2 gene amplification. RESULTS: The overall concordance between the two tests was 79.41% while the concordance between the two tests in equivocal cases, was 14.3%. ER/PR expression and HER-2 amplification were inversely associated. Also, Ki-67 expression was not associated with the side size of the lesion, lymphovascular invasion, and lymph node metastasis. Age less than 50 at presentation and infiltrating ductal carcinoma histological type showed increased proliferation index. CONCLUSION: The highest concordance between FISH and IHC was noted in IHC positive and negative cases, whereas IHC equivocal cases showed low concordance. FISH accurately determines the assessment of HER2 expressions in equivocal cases.