Human epidermal growth factor receptor 2 positive rates in invasive lobular breast carcinoma: The Singapore experience.

Background: Invasive lobular carcinomas (ILC) form 5%-10% of breast cancer and rarely show overexpression of human epidermal growth factor receptor 2 ().

Aim: To describe the prevalence and prognostic factors of positive () 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 status.

Results: A total of 864 patients were included. Prevalence of positivity was 10.1% (87 patients). Compared with negative () ILC, ILC was associated with a higher proportion of estrogen receptor negative (24.4% 5.9%, < 0.001), progesterone receptor negative () (40.2% 24%, = 0.002) and grade 3 tumours (Grade 3, 29.0% 10.2%, < 0.001). Overall survival rate was poorer in patients with compared to ILC (56.7% 72.9% alive at 10 years; hazard ratio 1.87, 95% confidence interval: 1.21-2.90, = 0.004). Based on multivariate analysis, negative prognostic factors for overall survival included positivity, negativity, older age, Indian ethnicity and higher tumour stage.

Conclusion: Prevalence of ILC was 10.1%. ILC was more likely to have poorer prognostic features such as estrogen receptor negative, and higher tumour grade, and have a poorer survival.