Abstract
Objectives: Endocrine therapy reduces recurrence risk by 30% to 50% in estrogen receptor (ER)-positive breast cancer. The ER-positive threshold recommended by the American Society of Clinical Oncology/College of American Pathologists is 1% based on studies using the ER-6F11 antibody. ER-SP1 antibody has a higher sensitivity and is more widely used. Methods: We report interobserver concordance manually measuring ER in 264 breast cancers using ER-SP1 and 1D5 and 2 scoring methods (H-score and Allred score). Results: With both antibodies, 3% to 4% of cases have a low level of ER expression (1%-10%), more than previously reported (<1%). We find a high level of paired observer concordance with both antibodies and scoring methods (k = 0.892-0.943) with no significant difference with method of scoring. Despite excellent concordance, positive/negative discordance was almost 5% among 3 observers using either antibody, an underappreciated clinically significant rate. Conclusions: Discordance overwhelmingly reflected differing opinions recording the proportion of tumor cells positive with low levels of expression (<10% staining; 12/13 cases).
Original language | English (US) |
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Pages (from-to) | 487-494 |
Number of pages | 8 |
Journal | American journal of clinical pathology |
Volume | 140 |
Issue number | 4 |
DOIs | |
State | Published - Oct 2013 |
Externally published | Yes |
Keywords
- Breast carcinoma
- Concordance
- Estrogen receptor
- Immunohistochemistry
ASJC Scopus subject areas
- Pathology and Forensic Medicine