Detection of HER2 protein in imprint cytology of invasive breast cancer

Objective: We studied detection of human epidermal growth factor receptor 2 (HER 2) protein in imprint cytology of invasive breast cancer and assessed the need for epitope retrieval and criteria for interpreting staining results. Study Design: In 35 cases of invasive breast cancer, HER2 protein status was assessed in imprinted cytology specimens (alcohol-fixed) and corresponding tissue sections (formalinfixed and paraffin-embedded). Immunohistochemistry assay for HER2 protein expression was done based on the Hercep Test protocol. Cytology specimens pretreated with and without heatinduced epitope retrieval were evaluated based on Hercep Test criteria (quality-based) and modified Hercep Test criteria (quantity-based), and results were compared to those for tissue sections. Results: A significant relationship was seen between HER2 status assessment in cytology specimens and tissue sections, without regard to heat-induced epitope retrieval or interpretation criteria for staining results. Quantity-based assessment of cytology specimens with no epitope retrieval approximates to that of tissue sections. Conclusion: The detection of HER2 protein in cytology specimens from breast cancer is possible, and quantity-based assessment of cytology specimens with no epitope retrieval is appropriate.