HER2 Protein Overexpression in Gastric Adenocarcinoma: The Relationship between Its Histological and Immunohistochemical Profiles in a Japanese Population
Koji Nagata, Michio Shimizu. Saitama Medical University, International Medical Center, Hidaka, Saitama, Japan
Background: Cases of gastric cancer with HER2 gene amplification and protein overexpression are treated by trastuzmab, and the frequency of these cases is reported to be 10-40% of gastric cancer. However, sufficient investigation has not been conducted regarding which histological types are found in cases of gastric cancer with HER2 expression. Therefore, we examined the frequency and the correlation between the histological types in HER2-expressing gastric cancers in Japanese patients.
Design: We reviewed a pathology database and collected all of the gastrectomy cases from April 2007 to June 2011. Then, a total of 132 consecutive cases were examined for their histological types and immunohistochemical HER2 expression. HER2 immunoreactivity was graded on a scale from 0 to 3 according to the ToGA study criteria. Cases with HER2 expression of 2+ or more were considered to possess HER2 expression. We classified the histologic types based on Lauren's classification and the Japanese cancer classification.
Results: The number of cases in each histological type is shown in Table 1.