[714] 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.

The number of HER2 expression cases in each histological type

The intestinal type of Lauren's classification includes pap, tub1 and tub2; the diffuse type includes por1, por2, muc-w, muc-p, sig and NEC. HER2 expression was significantly higher in the intestinal type of Lauren's classification (intestinal type, 18 out of 77cases, 23.5%; diffuse type, 3 out of 55 cases, 5.5%; overall, 21 out of 132 cases, 15.9%) and the papillary type in the Japanese classification (7 out of 11 cases; 63.6%). Significantly higher HER2 overexpression was noted in gastric cancers located at the distal stomach.
Conclusions: HER2 positivity was significantly higher in the intestinal type of Lauren's classification, and especially in the papillary type in the Japanese classification. It is interesting that the papillary type of gastric cancer is commonly observed in the proximal region of the stomach, and also that gastric cancer with the higher HER2 overexpression was frequently noted in the proximal portion of the stomach.
Category: Gastrointestinal

Tuesday, March 20, 2012 1:00 PM

Poster Session IV # 59, Tuesday Afternoon


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