Assessing the New American Society of Clinical Oncology/College of American Pathologists Guidelines for HER2 Testing by Fluorescence In Situ Hybridization: Experience of an Academic Consultation Practice

作者：Press Michael F^*; Villalobos Ivonne; Santiago Angela; Guzman Roberta; Cervantes Monica; Gasparyan Armen; Campeau Anaamika; Ma Yanling; Tsao Wei Denice D; Groshen Susan

来源：Archives of Pathology & Laboratory Medicine, 2016, 140(11): 1250-1258.

DOI：10.5858/arpa.2016-0009-OA

Context.-Evaluation of HER2 gene amplification by fluorescence in situ hybridization (FISH) was changed by recent American Society of Clinical Oncology/College of American Pathologists (ASCO-CAP) guidelines.
Objective.-To determine frequencies and assess patterns of HER2 protein expression for each ASCO-CAP guideline FISH category among 7526 breast cancers accrued to our consultation practice.
Design.-We retrospectively reevaluated the HER2 FISH status of breast cancers in our consultation practice according to ASCO-CAP FISH guidelines, and documented HER2 protein levels in each category.
Results.-According to new guidelines, 17.7% of our consultation breast cancers were "ISH-positive'' with HER2: CEP17 FISH ratios > 2.0 and average HER2 gene copies per cell >= 4.0 (group 1); 0.4% were "ISH-positive'' with ratios > 2.0 and average copies >= 4.0 (group 2); 0.6% were "ISH-positive'' with ratios > 2.0 and average copies >= 6.0 (group 3); 4.6% were "ISH-equivocal'' with ratios > 2.0 and average copies >= 4.0 and < 6.0 (group 4); and 76.7% were "ISH-negative'' with ratios > 2.0 and average copies >= 4.0 (group 5). However, only groups 1 (HER2 amplified) and 5 (HER2 not amplified) agreed with our previously reported status, and only these groups demonstrated the expected immunohistochemistry status, overexpression and low expression, respectively. Groups 2 and 4 breast cancers lacked overexpression, whereas group 3 was not significantly associated with either increased or decreased HER2 expression.
Conclusions.-Although the status of approximately 95% of our cases (groups 1 and 5) is not affected by the new guidelines, those of the other 5% (groups 2-4) conflict with previous HER2 gene amplification status and with HER2 status by immunohistochemistry.

• 出版日期2016-11