Minimum Formalin Fixation Time for Consistent Estrogen Receptor Immunohistochemical Staining of Invasive Breast Carcinoma

Abstract

To identify the minimum time necessary for consistent immunohistochemical estrogen receptor (ER) results in our laboratory, we evaluated results in timed fixation blocks and cases with disparate and similar needle core biopsy and partial mastectomy specimens. Tissue sections of 24 ER-positive, invasive breast carcinomas were fixed for 3, 6, 8, and 12 hours and 1, 2, and 7 days. ER values were quantified using the Q score (0-7). In timed fixation blocks, the mean Q score per block was 2.46 for blocks fixed for 3 hours, 5.75 for blocks fixed for 6 hours, and 6.70 for blocks fixed for 8 hours (P < .001). The difference between the case maximum and mean block Q scores was a plateau of almost 0 at 6 to 8 hours of formalin fixation. For needle core biopsy specimen fixation times, the means for specimens with ER-disparate and ER-similar results were 1.2 and 6.3 hours, respectively (P = .01). The minimum formalin fixation time for reliable immunohistochemical ER results is 6 to 8 hours in our laboratory, regardless of the type or size of specimen.

The reliability of assessment of oestrogen receptor expression on needle core biopsy specimens of invasive carcinomas of the breast

“…Adequate fixation is essential for reliable oestrogen receptor immunohistochemistry, with a minimum of 6-8 h of fixation required for consistent results. 14 The slightly higher H score on excision than core specimens in this and another study is consistent with superior fixation in the core specimen. 13 It appears that the discrepancy between the core and the subsequent excision biopsy can only rarely be attributed to the immunohistochemical technique as identical results were obtained on repeat staining in all except one specimen.…”

Brief fixation enables same-day breast cancer diagnosis with reliable assessment of hormone receptors, E-cadherin and HER2/Neu

“…Furthermore, data available on the effect of briefly fixed CNB on ER expression showed results analogous to ours, although most of these studies had a small sample size, with only highly expressing tumours included 13–17. Only one study25 stated that the minimum formalin fixation time should be at least 6–8 hours in order to maintain reliable results for ER expression, regardless of type or size of the specimen. This study however included a small sample size, had an extra processing step in which samples were temporarily stored in 100% ethanol after fixation and there was no precise account of the cold ischaemia time.…”

Technical pitfalls potentially affecting diagnoses in immunohistochemistry

“…Specifically, under-fixation in formalin can affect oestrogen receptor determination in breast cancer and a minimum fixation time of 6 hours is regarded as mandatory for obtaining reliable results 142. …”