Changes in human epidermal growth factor receptor 2 status between primary breast/gastric carcinomas and synchronous metastatic lymph nodes: how can we explain them?

Aim:Previous studies demonstrated discordant expression of human epidermal growth-factor receptor 2(HER2)between primary cancer and their recurrence/metastasis.This study further evaluated HER2 status between primary gastric and breast invasive carcinomas and paired metastatic disease to lymph nodes.Methods:This study collected formalin-fi xed paraffi n-embedded representative tissue blocks from 62 gastric and 65 breast primary carcinomas as well as synchronous metastatic lymph nodes(male:female=39:88;age ranged between 44 and 95 years with mean age of 69.32 years)for immunohistochemical staining of HER2 expression(DAKO HercepTest^(TM)kit).If immunohistochemical HER2 score reached to 2+,HER2 amplifi cation was then assessed using fl uorescence in situ hybridization(PharmDx^(TM)kit DAKO).Results:The discordant HER2 pooled rate,regardless either negative or positive conversion,was 9.67%in primary gastric carcinoma and corresponding nodal metastasis,while the changes in HER2 expression were revealed in 4.61%of mammary and lymph node neoplastic samples.A high-level concordance in HER2 expression between primary carcinoma and synchronous metastatic lymph nodes was confi rmed in both types of cancer;the observed event of discordant HER2 status should be ascribed to intra-tumor heterogeneity,mostly appreciable in gastric cancer.Conclusion:In any case,the shift from positive to negative HER2 expression suggests that trastuzumab could be the targeted treatment choice whereas the opposite shift should be evaluated by a simultaneous HER2 determination in both primary and metastatic lymph nodes.