Image cytometric HER2 in gastric carcinoma: is a new algorithm needed?

Area of Science:

• Oncology
• Pathology
• Biotechnology

Background:

• HER2 (human epidermal growth factor receptor 2) quantitation algorithms were initially developed for breast carcinoma.
• Gastric carcinoma HER2 assessment differs in required staining patterns (basolateral or lateral) compared to breast cancer's complete membrane positivity.
• Visual and image cytometry methods were compared for HER2 evaluation in gastric cancer, alongside fluorescence in situ hybridization (FISH).

Purpose of the Study:

• To compare visual and image cytometry results for HER2 quantitation in gastric cancer specimens.
• To assess the concordance of these methods with HER2 FISH results.
• To determine if the existing image cytometry algorithm for breast cancer needs modification for gastric cancer analysis.

Main Methods:

• Sixty-eight gastric carcinoma specimens (biopsies, resections, cell blocks) were analyzed.
• HER2 expression was evaluated visually and by image cytometry (ACIS score).
• FISH was performed on specimens with equivocal or positive scores (2+ or 3+) from image cytometry.

Main Results:

• A high concordance rate was observed between visual and image cytometry for HER2 assessment (93% for positive, 98% for negative).
• HER2-positive cases by IHC (visual or cytometry) showed 100% concordance with HER2 amplification by FISH.
• HER2 positivity was most frequent in poorly differentiated gastric cancers, though not significantly.

Conclusions:

• Visual and image cytometry methods demonstrate high concordance with FISH for HER2 evaluation in gastric cancer.
• The current image cytometry algorithm used for breast cancer is suitable for assessing HER2 in gastric cancer without modification.
• The findings support the reliability of image cytometry for HER2 testing in various gastric cancer specimen types and differentiation levels.