Building consistency in HER2 IHC assessment of gastric cancer

Building consistency in
HER2 IHC assessment
of gastric cancer

Clinical Significance of HER2 in Gastric Cancer

Clinical significance of HER2 in gastric cancer

With the potential to inform treatment options, HER2 testing is of vital importance in enabling us to learn more about patients' gastric cancer.1 To support HER2 IHC clinical practice, the ASCO-ASCP-CAP joint committee have published extensive testing guidelines, which cover pre-analytics, scoring, and reporting recommendations.1

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How does HER2 in gastric cancers differ from breast?

 

Membranous distribution of antibody

Breast Table IconBreast

Predominantly circumferential in IHC 3+2,3

Gastric Cancer IconGastric

Can be basolateral or lateral in IHC 3+1,2

Intratumoral heterogeneity

Breast

Less commonly encountered4

Gastric

More commonly encountered4

Location dependent variation in
HER2
expression

Does not occur2

More frequent in the proximal stomach
relative
to distal2

Gastric HER2 IHC scoring algorithm

ASCO-ASCP-CAP guidelines recommend the following scoring algorithm for gastric cancers, which define separate scoring criteria for surgical and biopsy specimens.

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Gastric HER2 IHC Scoring Algorithm

*Tumor cell cluster (≥5 neoplastic cells).

Images supplied by Discovery Life Sciences, Inc.

Adapted from Bartley, et al. J Clin Oncol. 2017;35(4):446-464.

Testing and reporting guidelines

Microscope Icon Testing method

IHC with reflex to ISH for equivocal (IHC 2+) results.1

Report Icon Reporting

CAP have published a template for gastric HER2 biomarker reporting5

List Icon Key reporting elements

  • Discrete HER2 IHC score5
  • HER2 (ERBB2) ISH result5
  • HER2 (ERBB2) genomic test results5
  • Methods5

gastric overview flowchart

*Tumor cell cluster (≥5 neoplastic cells).
Images supplied by Discovery Life Sciences, Inc.

Adapted from Bartley, et al. J Clin Oncol. 2017;35(4):446-464.

 

ASCO, American Society of Clinical Oncology; ASCP, American Society for Clinical Pathology; CAP, College of American Pathologists; ERBB2, erythroblastic leukemia viral oncogene homolog 2; GEA, gastroesophageal adenocarcinoma; HER2, human epidermal growth factor receptor 2; IHC, immunohistochemistry; ISH, in situ hybridization.

1. Bartley AN, et al. J Clin Oncol 2017;35(4):446-464. 2. Abrahao-Machado LF and Scapulatempo-Neto C. World J Gastroenterol 2016;22(19):4619-4625. 3. Wolff AC, et al. Arch Pathol Lab Med 2023;147(9):993-1000. 4. Kaito A, et al. World J Clin Cases 2019;7(15):1964-1977. 5. CAP. Template for Reporting Results of HER2 (ERBB2) Biomarker Testing of Specimens from Patients with Adenocarcinoma of the Stomach or Gastroesophageal Junction. Version 1.0.0.1. Accessed: January 2024. Available at: https://documents.cap.org/protocols/cp-gastric-HER2biomarker17-1001.pdf.

Clinical Significance of HER2 in Gastric Cancer
Clinical Significance of HER2 in Gastric Cancer

Gastric Cancer Resources

Discover educational materials on HER2 testing in gastric cancer designed to support your clinical practice.

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