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Impact of the 2013 A merican S ociety of C linical O ncology/ C ollege of A merican P athologists guideline recommendations for human epidermal growth factor receptor 2 ( HER 2) testing of invasive breast carcinoma: a focus on tumours assessed as ‘equivocal’ for HER 2 gene amplification by fluorescence in‐situ hybridization
Author(s) -
Bethune Gillian C,
Veldhuijzen van Zanten Daniel,
MacIntosh Rebecca F,
Rayson Daniel,
Younis Tallal,
Thompson Kara,
Barnes Penny J
Publication year - 2015
Publication title -
histopathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.626
H-Index - 124
eISSN - 1365-2559
pISSN - 0309-0167
DOI - 10.1111/his.12723
Subject(s) - medicine , breast cancer , human epidermal growth factor receptor 2 , pathological , oncology , cancer
Aims The updated 2013 American Society of Clinical Oncology/College of American Pathologists ( ASCO / CAP ) human epidermal growth factor receptor 2 ( HER 2) testing guidelines include changes to HER 2 in‐situ hybridization ( ISH ) interpretation criteria. We conducted a retrospective review of a consecutive cohort of primary breast carcinomas to assess the impact of updated guidelines on HER 2 classification and laboratory resource utilization, and to characterize the pathobiology of HER 2 equivocal tumours. Methods and results A total of 904 dual‐probe HER 2/chromosome enumeration probe ( CEP 17) FISH tests on invasive breast carcinomas were studied. Eighty‐five (9.4%) cases had a classification change with the updated guidelines; 66 (7.3%) went from HER 2‐negative to ‐equivocal, 15 cases (1.7%) were reclassified as HER 2‐positive and four cases from HER 2‐equivocal to ‐negative. A subset of primary breast cancers, reported initially as HER 2‐negative but ‐equivocal by 2013 guidelines, was identified. Traditional pathological factors of this subset were compared to HER 2‐negative and ‐positive control cases. The three HER 2 groups demonstrated statistically significant differences with respect to prognostic factors, including tumour size, grade and nodal involvement. Conclusions The updated HER 2 testing guidelines will result in the reclassification of approximately 9.4% of primary breast cancers with uncertainty regarding the clinical impact of this reclassification in the majority of cases. Resource utilization will increase as a result of the recommendation for retesting.