A potential pitfall in evaluating HER2 immunohistochemistry for gastric signet ring cell carcinomas

Chang Gok Woo, Won Jin Ho, Young Soo Park, Sook Ryun Park, Min Hee Ryu, Hwoon Yong Jung, Yoon Koo Kang

Research output: Contribution to journalArticlepeer-review

Abstract

Signet ring cell carcinoma (SRC) more commonly presents as metastatic disease and renders patients to be considered for chemotherapy. While treatment options are limited overall, trastuzumab has been shown to be effective for HER2 positive SRC cases. The current algorithm for HER2 evaluation heavily relies on positive membrane-specific staining by immunohistochemistry (IHC), but several anecdotal reports have suggested that SRCs may be susceptible to misinterpretation due to non-specific staining in the marginated cytoplasm with/without nucleus. Results of two FDA-approved IHC methods of HER2 evaluation, Pathway and HercepTest, along with silver in situ hybridisation were interpreted retrospectively and compared in 155 primary SRC cases. IHC results were discrepant between the two assays in SRC even at the strongest IHC scores. Discordance indeed occurred due to dark, non-specific staining obscured by the unique SRC morphology. True HER2 positive SRC was identified in three cases (3/155, 1.9%). In this study, we demonstrate the importance of recognising potential discrepancy in interpreting HER2 status depending on the assay used. Understanding this possible pitfall may prevent unnecessary trastuzumab in SRC patients.

Original languageEnglish (US)
Pages (from-to)38-43
Number of pages6
JournalPathology
Volume49
Issue number1
DOIs
StatePublished - Jan 1 2017
Externally publishedYes

Keywords

  • Gastric cancer
  • HER2
  • immunohistochemistry
  • signet ring cell carcinoma
  • trastuzumab

ASJC Scopus subject areas

  • Pathology and Forensic Medicine

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