Background : The prognosis of Gallbladder cancer (GBC) is poor prognostic disease despite conventional multimodal treatment. Therefore, research on new targeted therapeutic options is required. We investigated the humane epidermal growth factor receptor 2 (HER2) status according to breast and stomach guideline and its clinicopathological differences in T2 gallbladder cancer (GBC).

Methods : We evaluated HER2 expression in T2 GBC 90 cases who underwent radical cholecystectomy by immmunohistochemistry (IHC). And we analyzed prognostic factors including HER2 2+ and 3+ in T2 GBC.

Results : The HER2 score was 0 in 72/90 (80.0%), 1+ in 8/90 (8.88%), 2+ in 5/90 (5.56%) and 3+ in 5/90 (5.56%) cases according to stomach cancer guideline. HER2 score was 0 in 82/90 (91.11%), 1+ in 0/90 (0%), 2+ in 3/90 (3.33%) and 3+ in 5/90 (5.56%) cases according to breast cancer guideline. The 5-year disease-free survival (DFS) and overall survival (OS) rates were 74.8% and 70.6%. Multivariate analyses for DFS showed that poorly differentiation and higher level of perineural invasion were identified as significant independent factors. Multivariate analyses for OS survival showed that old age, man, presence of lymph node metastasis, poorly differentiation, higher level of perineural invasion and high HER2 score (2+ and 3 + in IHC) based on breast cancer guideline.

Conclusions : In curative resected T2 GBC, poorly differentiation and higher level of perineural invasion were a significant independent prognostic factor in disease-free survival and overall survival. As HER2 2+ and 3+ according to the breast cancer guideline showed a correlation with overall survival, we hope it will be a reference when considering anti-HER2 therapy.