[135] Concordance between Tissue Microarray and Whole Section Estrogen Receptor Expression and Intratumoral Heterogeneity

Leah Dvorak, Roberto Gamez, Linda Varghese, Colleen Forster, H Evin Gulbahce. University of Minnesota Fairview, Minneapolis, MN; Mayo Clinic, Rochester, MN; Fairview Southdale Hospital, Edina, MN; BioNet, University of Minnesota Fairview, Minneapolis, MN; VA Medical Center, Minneapolis, MN

Background: Hormone receptor status determination for breast cancer is an important part of pathologists' daily sign outs and many retrospective and prospective studies. We compared the estrogen receptor (ER) expression tested on tissue microarray (TMA) sections to those tested on whole sections (WS) to find out concordance and frequency of intratumoral heterogeneity (ITH).
Design: One mm TMA were constructed from breast cancer excision tissue which were originally tested for ER by IHC or ligand binding assay (LBA). Discrepancy in ER expression between WS and TMA was evaluated only on those originally tested with IHC. All cases (origianlly tested by both IHC and LBA) with large enough tumor available on the block to allow more than 1 core were used to determine ITH. Each core's ER status was independently determined according to the current CAP guidelines with ≥% staining recorded as positive. Staining intensity was not evaluated.
Results: 15 of 272 (5.5%) of the cases showed discrepant results between WS and TMA. Likelihood of finding discrepancy between TMA and WS decreased as more cores were available at TMA. Overall 5/66 (7.6%) of TMA ER negative cases and 10/206 (4.9%) of TMA ER positive cases showed discrepancy with WS ER results. Four of 279 (1.4%) cases with more than one core on TMA (three cases had 3 cores and one case had 4 cores on TMA) showed discrepancy amongst the cores.
Conclusions: There is good correlation between ER on WS IHC and TMA IHC. TMA, rather than WS, may be used for ER status determinations from old stored blocks which were originally tested with LBA or IHC but need to be retested with a different Ab. This also provides indirect evidence that in majority of the cases, ER results of breast core biopsies will be representative of the whole tumor which is important in patients undergoing neoadjuvant therapy with no residual invasive tumor to test or confirm biopsy ER results. Intratumoral ER expression heterogeneity within the same tumor block is a rare event within primary breast cancers. Since only four of the 279 (1.4%) cases which had more than 1 core available showed discrepancy amongst the cores, it is not possible to recommend the optimal number of cores for accurate classification of a case as ER negative.
Category: Breast

Monday, March 19, 2012 1:00 PM

Poster Session II # 55, Monday Afternoon

 

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