Study on molecular subtypes and correlation between molecular subtypes and histopathological features in invasive breast cancer

Background: To determine the molecular subtypes and correlation between molecular subtypes and histopathological features in breast cancer in Vietnam and Italy. Material and method: 88 patients with invasive breast carcinoma (BC) in both Hue Central Hospital and Hue University Hospital in Vietnam during 1 year from April 2016 to April 2017 as well as 235 patients from the same category of women in Sassari University Hospital, Italy during the year 2016 were collected. All patients were examined for immunohistochemistry (IHC) with four markers ER, PR, HER2, and Ki67. The immunofluorescence in situ hybridization (FISH) test was applied for cases with HER2 (2+)/ IHC. Results: Breast cancer in Vietnam had the highest Luminal B (LB) rate, at 37.5%, followed by HER2 enrich (22.7%) and triple-negative breast cancer accounting for 21.6%. Luminal A (LA) accountd for the lowest proportion (18.2%). In contrast, breast cancer in Italy has the highest rate of Luminal A (54%), LB accounted for 34.5%, triple-negative occupied 10.6% and HER2 enrichment has a very low rate (0.9%). There was a statistically significant correlation between molecular subtypes and pathological features such as histologic grade, axillary lymph node, and stage of disease in both Vietnamese and Italian groups (p<0.005). Most breast cancers in Vietnam and Italy belong to the Luminal A with low histologic grade, early-stage disease, and no metastasis. No statistically significant association was found between molecular subtypes and tumor size in the Vietnamese breast cancer group. By contrast, this association was statistically significant with p<0.05 in Italy. Conclusion: There is a significant difference in the molecular subtypes and the correlation between molecular subtypes and histopathological features between Vietnamese and Italian breast cancers. The two more common subtypes in Vietnam are LB and HER2, while in Italy they are LA and LB. The rate of HER2 subtypes in Vietnam is much higher than in Italy Key words: Invasive breast carcinoma, molecular subtype, Vietnam, Italy