American Society of Clinical Oncology/College of American Pathologists Guidelines Should Be Scientifically Validated

To the Editor.—Although I agree with the majority of the “American Society of Clinical Oncology/College of American Pathologists Guideline Recommendations for Human Epidermal Growth Factor Receptor 2 Testing in Breast Cancer” by Wolff et al,1 I am concerned with the sample exclusion criteria for human epidermal growth factor receptor 2 (HER2) immunohistochemistry (Table 5, p 27), both as they relate to the issue at hand and for the precedent this list of guidelines sets in an area of pathology certain to see more regulation.The American Society of Clinical Oncology/College of American Pathologists panel delineated optimal formalin fixation time for HER2 immunohistochemistry performed on excisional biopsies as 6 to 48 hours. Furthermore, the panel mandates that a negative HER2 result from suboptimal specimens (ie, those fixed less than 6 hours or longer than 48 hours) should be qualified in the report. It is intuitive that grossly underfixed breast tissue is not an optimal specimen for HER2 testing, but experience demonstrates that routine weekend fixation (up to 72 hours) allows for good preservation of a wide range of antigens provided appropriate heat-induced epitope retrieval is used. A study by Arber2 analyzing HER2 antigen preservation after prolonged formalin fixation (7–154 days) found no change in immunoreactivity for up to 20 days in tissues from 33 different infiltrating breast carcinomas. This author has evaluated HER2 antigen preservation in 20 infiltrating breast carcinomas after 7 to 14 days of formalin fixation and observed undiminished strong membranous staining after heat-induced epitope retrieval (unpublished data). Boenisch3 has shown convincingly that heat-induced epitope retrieval can restore immunoreactivity after prolonged formalin fixation. Twenty-nine of 30 antigens tested showed equivalent staining intensity after 4 days of formalin fixation. A recent review by Goldstein et al,4 entitled “Recommendations for Improved Standardization of Immunohistochemistry,” suggests a minimum formalin fixation time of 8 hours (recommendation 1). No maximum fixation time is recommended, and it is stated that “In general, underfixation is a substantially larger problem than overfixation.” (p126)Reading the Archives article in question I failed to discover any referenced study supporting the sample exclusion criteria. The authors simply allude to previous consensus conferences dealing with HER2 testing (Appendix E). Subsequently, Patrick Fitzgibbons, MD, an author of the guideline article1 and chair of the College of American Pathologists Immunohistochemistry Committee, acknowledged to me in an e-mail (March 2007) that studies confirming the hour-by-hour impact of formalin fixation on HER2 testing over the range of fixation intervals seen in clinical practice have not been completed. It is axiomatic that promulgated guidelines should be evidence based and scientifically validated. In the absence of peer-reviewed study in its support, adoption of the greater than 48-hour formalin fixation exclusion criterion would be counterproductive. This is especially true in light of the potential impact of said criterion on current laboratory practice (ie, necessitating staffing histology on the weekend to accommodate Friday morning breast cancer surgeries). Based on the evidence cited herein, a 72-hour maximum fixation exclusion criterion would be more appropriate, allowing for routine weekend fixation while enabling accurate and reproducible HER2 testing.The author has no relevant financial interest in the products or companies described in this article.This letter has been jointly published by consent in the Archives and CAP Today.