Background
- Immunohistochemical (IHC) staining is the primary method of HER2 assessment in solid malignancies at many institutions. Approved algorithms with differing scoring parameters exist for HER2 in breast and gastric carcinomas1-2.
- Historically, a binary categorization of HER2 status (positive vs. negative) defined the treatment of patients with HER2-expressing tumors based on the activity of trastuzumab3.
- The development of HER2 antibody-drug conjugates (ADCs) has provided evidence of anti-tumor activity in cancers across a full range of HER2 expression, including equivocal staining3-4.
- Enrollment in recent clinical trials was based on HER2 diagnostic criteria for gastric carcinoma4, while breast cancer scoring algorithms are commonly used for HER2 assessment in gynecologic malignancy5-6.
- Neither breast nor gastric scoring system has been validated in gynecologic neoplasms. Our study seeks to assess the concordance among immunohistochemical (IHC) scoring for HER2 expression in endometrial cancer when gastric versus breast HER2 diagnostic criteria are used.