Original ResearchPathological characterisation of male breast cancer: Results of the EORTC 10085/TBCRC/BIG/NABCG International Male Breast Cancer Program

- We describe the largest male breast cancer series with central pathology review.
- Lobular breast cancer is rare in male.
- Histological grade was not associated with outcome, unlike what is known in females.
- Mitotic-index, presence of fibrosis and lymphocytes correlated with outcome.

AimSeveral prognostic histological features have been established in female breast cancer (BC), but it is unknown whether these can be extrapolated to male BC patients. The aim of this study was to evaluate the prognostic value of several histological features in a large series of male BC.MethodsCentral pathology review was performed for 1483 male BCs collected through part 1 of the European Organisation for Research and Treatment of Cancer (EORTC) International Male BC Program. Pathology review included histological subtype, grade, mitotic activity index (MAI), presence of a fibrotic focus and density of tumour-infiltrating lymphocytes (TILs). These features were correlated with clinical outcome. The relationship between these features and surrogate molecular subtypes using immunohistochemistry was also assessed.ResultsMedian follow-up for overall survival (OS) was 7.1 years. Overall histological grade was not significantly associated with OS (p = 0.129). MAI, the presence of a fibrotic focus and a low TIL density however were correlated with unfavourable OS (p = 0.023, p = 0.004 and p = 0.011, respectively). BC subtype correlated with TIL density (p = 0.015), as we observed a higher density for human epidermal growth factor receptor type 2 (HER2) positive BC compared to luminal HER2-negative subtype. No association was observed between subtype and fibrotic focus.ConclusionsHistologic grade was not significantly correlated with clinical outcome in this series, unlike what is seen in female patients. These results contribute to our understanding of male BC and indicate the importance of further research on the optimisation of risk stratification and treatment decisions for male BC patients.