Clinicopathological features and endoscopic findings of HER2-positive gastric cancer.

BACKGROUND: Human epidermal growth factor receptor 2 (HER2) expression in gastric cancer is highly heterogeneous. Therefore, it is important to take endoscopic samples from appropriate tumor sites.

METHODS: Between January 2008 and April 2015, patients with gastric or gastroesophageal junction cancer with histologically confirmed adenocarcinoma were included. Surgical samples or endoscopic biopsy samples were examined for HER2 using immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). Tissues were considered to be HER2 positive when either assessment revealed either an IHC score of 3+ or an IHC score of 2+ accompanied by a positive FISH result. Endoscopic findings were retrieved in all cases where available, and we examined the portion from which a biopsy was obtained.

RESULTS: Out of the 612 patients included in the study, 104 (17%) were HER2 positive. The proportion of HER2-positive gastric tumors with differentiated (vs. undifferentiated) histology was significantly higher (29 vs. 6%, respectively; p < 0.001). The HER2-positive rate of papillary adenocarcinomas (vs. tubular) was particularly high (62%, 8/13; p = 0.023). The proportion of HER2-positive gastric tumors of Borrmann classification 0 or 1 was significantly higher than that of tumors of classified as 2, 3, or 4 (45 vs. 16%, respectively; p < 0.001). The HER2-positive rates per biopsy specimen from the superficial spreading portion, ulcer mound, ulcer bed, and mass portion were 100, 91, 45, and 100%, respectively.

CONCLUSIONS: HER2-positive gastric cancer tends to be associated with a differentiated histology, particularly papillary adenocarcinoma, and a Borrmann classification of 0 or 1 tumors. Based on these endoscopic findings, it is important to recognize the superficial spreading portion and the mass portion of gastric malignancies.