Breast Biomarkers-Comparison on Whole Section and Tissue Microarray Section.

Abstract

Estrogen Receptor (ER), Progesterone Receptor (PR) and Her2/neu are routinely studied markers for breast carcinoma. Analysis of these biomarkers is traditionally done by Immunohistochemistry (IHC) on whole sections. These markers can also be studied on Tissue Microarray (TMA) sections. Tissue microarray is a technique where core samples from different paraffin blocks are arrayed on a single recipient block which can then be cut to yield a single section with multiple cores in it. To compare ER, PR and Her2/neu on TMA sections with whole sections and to determine the concordance of results between the two methods. A TMA block was constructed by punching out 2 mm cores from appropriately marked paraffin blocks of 53 breast carcinoma cases and embedding them in the recipient block. Immunostaining of TMA sections and whole sections were performed for ER, PR and Her2/neu and the results were compared. Statistical analysis was done using chi square test/Fisher-Exact test. Kappa co-efficient, Jaccard Index and G-Index were computed. Infiltrating Ductal Carcinoma-No Special Type (IDC-NST) was the predominant type of carcinoma and most of the tumours were of Grade II and III. Majority, 38/53 (71.7%) were ER/PR positive and Her2 negative and 9/53 (17%) cases were triple negative. Good concordance between whole sections and TMA sections were noted with kappa value for ER, PR and Her2/neu being 0.671, 0.754, 1.000 respectively which was statistically significant. Immunostaining for ER, PR and Her2/neu done on TMA section using single 2 mm core were comparable with conventional whole section scores. Thus, TMA is a reliable method for evaluating these biomarkers with the advantage of being time and cost effective.