BACKGROUND Invasive lobular carcinomas (ILC) form 5%-10% of breast cancer and rarely show overexpression of human epidermal growth factor receptor 2 ( HER2 ). AIM To describe the prevalence and prognostic factors of HER2 positive ( HER2+ ) ILC in an Asian population. METHODS A retrospective review of patients with ILC seen between January 1985 and March 2018 at various SingHealth medical institutions was conducted. Demographic and clinical data were collected from medical records. We examined clinicopathological characteristics and survival in relation to HER2 status. RESULTS A total of 864 patients were included. Prevalence of HER2 positivity was 10.1% (87 patients). Compared with HER2 negative ( HER2- ) ILC, HER2+ ILC was associated with a higher proportion of estrogen receptor negative (24.4% vs 5.9%, P < 0.001), progesterone receptor negative ( PR- ) (40.2% vs 24%, P = 0.002) and grade 3 tumours (Grade 3, 29.0% vs 10.2%, P < 0.001). Overall survival rate was poorer in patients with HER2+ compared to HER2- ILC (56.7% vs 72.9% alive at 10 years; hazard ratio 1.87, 95% confidence interval: 1.21-2.90, P = 0.004). Based on multivariate analysis, negative prognostic factors for overall survival included HER2 positivity, PR negativity, older age, Indian ethnicity and higher tumour stage. CONCLUSION Prevalence of HER2+ ILC was 10.1%. HER2+ ILC was more likely to have poorer prognostic features such as estrogen receptor negative, PR- and higher tumour grade, and have a poorer survival.

Background: TP53 mutation is the most common mutation in breast cancer, and it is considered a target marker of triple negative breast cancer (TNBC). The purpose of this study was to evaluate the prognosis of TNBC using only clinical information. The p53 status detected immunohistochemically was evaluated as a prognostic and predictive factor. Methods: Among KBCSR-registered patients, triple-negative breast cancer patients diagnosed between 2000 and 2015 were included. This included patients who were aged 20 years or older and had between stage I and stage III TNBC. A total of 11,393 patients were included in this study, including 6,331 'p53-positive TNBC' and 5,062 'p53-negative TNBC' cases. The median follow-up period was 60 months (1-188 months). Results: In univariate analysis, there was no difference in prognosis between p53þ TNBC and p53-TNBC for patients receiving chemotherapy. But, p53þ TNBC had a worse prognosis than p53-TNBC in patients not receiving chemotherapy (P ¼ 0.003). In multivariate analysis adjusted for age and cancer stage, the risk of p53þ TNBC was 1.84 times higher than that of p53-TNBC in the non-chemotherapy group. There was no difference between p53þ TNBC and p53-TNBC in patients receiving chemotherapy. In p53þ TNBC, the risk was 0.6-fold lower when chemotherapy was administered than when chemotherapy was not administered. In p53-TNBC, there was no risk reduction effect by chemotherapy. Conclusions: The prognosis of p53-TNBC is better than that of p53þ TNBC, but it shows no benefit of chemotherapy. p53þ TNBC has a poor prognosis but benefits from chemotherapy. In conclusion, p53þ TNBC appears to be more sensitive to chemotherapy than p53-TNBC.