Background: Breast cancer is the most common cancer and the second most common cause of death from cancer in women. HER2 is an epidermal growth factor receptor which plays a substantial role in pathogenesis of breast cancer and also a target for new antineoplastic drug Herceptin. This study was conducted for determining the correlation between HER2 overexpression and histopathologic characteristics of breast cancer and also degree of intraobserver and interobserver agreement in scoring of Immnohistochemistry (IHC) slides between pathologists in samples referred to pathology ward.
Methods: This study was conducted as a descriptive cross sectional study. Among the breast cancer samples referred to pathology ward in Shariati Hospital in Tehran, Iran. 140 samples have been selected sequentially using simple non-random sampling method. All the information has been extracted using medical records and pathology reports.
Results: This study showed significant difference between diagnosis and HER2 status (p<0.05). Significant difference observed between lymph node invasion and HER2 status (p<0.05). Positive significant association between the size and tumor grade with HER2 status (r=0.188, p=0.026), Significant difference between histopathologic types with scoring of HER2 (p=0.001). Significant difference between histopathologic types with lymph node invasion (p=0.001). Agreement level of HER-2 scoring was shown to be nearly perfect between two observers (kappa statistic= 0.715) and the same observer (Kappa statistic= 0.78).
Conclusion: We do not recommend IHC and FISH test in invasive lobular carcinoma of breast and uncommon subgroups of breast cancer except in invasive ductal carcinoma and its subgroups.