Brief Formalin Fixation and Rapid Tissue Processing Do Not Affect the Sensitivity of ER Immunohistochemistry of Breast Core Biopsies

Objectives: Recent studies have questioned the supporting evidence for the American Society of Clinical Oncology/ College of American Pathologists (ASCO/CAP) guidelines of the 8-hour minimum fixation time required for estrogen receptor immunohistochemistry (ER-IHC) assays in breast cancer. Methods: We investigated whether brief formalin fixation together with rapid tissue processing affects the sensitivity of ER in core breast biopsies. Five core samples each from 22 mastectomy specimens were collected and fixed in 10% formalin for periods ranging from 30 minutes to 1 week. Core 5 was fixed and processed according to the ASCO/CAP guidelines. ER-IHC was performed following heat-induced antigen retrieval using antibody 1D5. The proportion and intensity of reaction was recorded using the Q score. Results: Five of 22 cancers were ER negative in all cores. In 17 ER-positive cases, no differences were found in the intensity of reaction between 30 minutes and 1 week of formalin fixation. Similarly, no difference was observed in the Q scores of rapidly and conventionally processed control tumor cores. Conclusions: Brief formalin fixation along with rapid processing has no negative effect on the sensitivity of ER-IHC in breast core biopsies. This combination significantly reduces the turnaround time for preparing breast needle biopsy specimens. The decision to initiate treatment for patients with breast cancer is based on the results of tissue biomarker studies including estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). Breast core needle biopsy specimens are now the primary source for the performance of these tests, particularly if neoadjuvant therapy is being considered. Preanalytic variables may affect the accuracy of ER, PR, and HER2 results. Immunohistochemical detection of ER requires adherence to standardization of preanalytic variables including the cold ischemic time, type of fixative, and duration of fixation. 1-4 The guidelines of the