Introduction: Genetic profile studies of breast cancer identified a number of biologically different subtypes. These genetic subtypes are often surrogated by oestrogen receptors (ERs), progesterone receptors (PR) and HER2 status as measured by immunohistochemistry (IHC). Triple negative (TN) subtype is recognized to have high-risk features and poor outcome. Over-expression of the HER2 is also recognized as poor outcome marker. The characteristics and outcome of HER2 positive tumours (irrespective of hormonal status) (HER2 HR+/-) identified by IHC have not addressed in the era of surrogate genetic subtyping. Therefore, we retrospectively compared the risk features and clinical outcome of patients with TN against these with HER2 HR+/- tumours.

Patients and Methods: Forty patients with HER2 HR+/- tumours were matched for age and stage to 40 patients with TN tumours. Clinical and pathological data were collected retrospectively. All patients were managed in a single institution.

Results: Tumour grade and stage and rate of pathologically involved lymph nodes were similar in both groups. There was a trend of more lymphovascular invasion in HER2 HR+/- than TN patients (40% vs. 27.5%. p=0.07). Relapse and death rates were not statistically different (p=0.469 and p=1.0, respectively). Median relapse free survival was 38 months for TN and not reached for HER2 HR+/- patients (Log rank; p=0.757). Median overall survival was not reached in both groups. Multivariate analysis did not identify TN or HER2 HR+/- status to have any differential impact on RFS.

Conclusion: HER2 HR+/- tumours exhibit high risk, presenting features and relatively poor clinical outcome possibly not very different from the increasingly recognized TN tumour.