Human Epidermal Growth Factor Receptor 2 Overexpression in Micropapillary and Other Variants of Urothelial Carcinoma

Abstract

BackgroundHuman epidermal growth factor receptor 2 (HER2) protein overexpression or gene amplification has been shown in urothelial bladder cancer. This could be helpful when using targeted anti-HER2 therapy on these tumors. ObjectiveTo evaluate HER2 immunohistochemical expression in conventional urothelial carcinoma (UC), in situ UC, and UC variants primarily in micropapillary urothelial carcinoma (MPUC). Design, setting, and participantsThe study evaluated 60 MPUC cases; 25 invasive, 20 low-grade noninvasive, and 10 high-grade noninvasive UC cases; 8 in situ UC cases; and 69 UC variant cases. The immunohistochemistry staining was scored according to recommendations of the American Society of Clinical Oncology/College of American Pathologists 2013 HER2 test guideline established for breast cancer and only 3+ staining was considered HER2 overexpression. Outcome measurements and statistical analysisHER2 overexpression was determined by 3+ staining. Results and limitations34 of 60 MPUC cases (56%) showed HER2 overexpression (3+ staining). We observed 3+ staining HER2 overexpression in nine of 25 conventional invasive UC cases (36%), four of eight in situ UC cases (50%), and three of six lipid cell variant cases (50%). 3+ staining HER2 overexpression was not seen in eight glandular, six small cell, and five sarcomatoid variant cases. HER2 overexpression was negative in the 20 low-grade noninvasive UC cases but positive in two of the 10 high-grade noninvasive UC cases (20%). We observed HER2 overexpression most commonly in MPUC cases. We also found HER2 overexpression in conventional invasive and in situ UC cases. ConclusionsPure in situ UC and conventional invasive UC, especially MPUC, could be candidate tumors for treatment with anti-HER2 antibody (trastuzumab therapy). Patient summaryTargeted therapy has a limited place in treatment of bladder cancer. In this study, human epidermal growth factor receptor 2 (HER2) overexpression in bladder carcinomas was evaluated in a large number of cases. Anti-HER2 therapy could be used in bladder cancers, as in breast and gastric cancers.