The integration of genomic and transcriptomic profiles of 2000 breast tumours 
from the METABRIC [Molecular Taxonomy of Breast Cancer International Consortium] 
cohort revealed ten subtypes, termed integrative clusters (IntClust/s), 
characterised by distinct genomic drivers. Central histopathology (N = 1643) 
review was undertaken to explore the relationship between these ten molecular 
subtypes and traditional clinicopathological features. IntClust subtypes were 
significantly associated with histological type, tumour grade, receptor status, 
and lymphocytic infiltration (p < 0.0001). Lymph node status and Nottingham 
Prognostic Index [NPI] categories were also significantly associated with 
IntClust subtype. IntClust 3 was enriched for tubular and lobular carcinomas, 
the latter largely accounting for the association with CDH1 mutations in this 
cluster. Mucinous carcinomas were not present in IntClusts 5 or 10, but did not 
show an association with any of the remaining IntClusts. In contrast, 
medullary-like cancers were associated with IntClust 10 (15/26). Hormone 
receptor-positive tumours were scattered across all IntClusts. IntClust 5 was 
dominated by HER2 positivity (127/151), including both hormone receptor-positive 
(60/72) and hormone receptor-negative tumours (67/77). Triple-negative tumours 
comprised the majority of IntClust 10 (132/159) and around a quarter of IntClust 
4 (52/217). Whilst the ten IntClust subtypes of breast cancer show 
characteristic patterns of association with traditional clinicopathological 
variables, no IntClust can be adequately identified by these variables alone. 
Hence, the addition of genomic stratification has the potential to enhance the 
biological relevance of the current clinical evaluation and facilitate 
genome-guided therapeutic strategies.