Molecular cytogenetic evaluation of formalin-fixed paraffin embedded breast tumor tissue

Human epidermal growth factor receptor 2 (HER2) has been shown to be amplified in approximately 20-25% of human breast carcinomas, and is a significant predictor of both overall survival and time to relapse in patients with breast cancer. This study aimed to estimate HER2 gene status of cancer cases with immunohistochemically equivocal (2+) score using fluorescence in situ hybridization (FISH) technique.The study included 44 formalin-fixed paraffin embedded tissue blocks from female patients with invasive breast carcinoma with IHC 2+. Hormone receptors assessment also performed for all the enrolled cases. All cases were studied by FISH for the determination of the amplified HER2 gene. FISH technique showed that HER2 gene was not amplified in 33 cases out of 44 (75%); while the rest of cases 11 (25%) revealed amplified gene status. Among FISH positive cases there was 54.54% PR positive and 45.45% PR negative, 72.72% ER positive and 27.27% ER negative.Our result show when the threshold of ER/PRfor HER2 IHC 2+ cases was increased 10 % to 30 % of tumor cells with incomplete membrane staining; the HER2 gene amplification was increased concomitantly. When the threshold of ER/PR was increasedfor more than 30 % of tumor cells, there wasn’t any significant association between the result of FISH and the hormone receptors assessment. It seems that low amount (10% to 30%) of ER/PR in tumor cells correlates with amplification of HER2 and high amount (> 30%) of ER/PR might be related to the other molecular changes in tumorigenesis.

کلیدواژه ها:

Her2 ، breast cancer ، IHC ، ER/PR