Triple-negative breast cancers account for 12-17% of all invasive breast carcinomas and comprise a heterogeneous group of tumours, with varying histological features and clinical behaviours. Focal apocrine differentiation can be associated with a subset of these lesions. To establish whether morphological diversity is associated with divergent genetic aberrations the genomic profiles of microdissected, morphologically distinct components from an invasive ductal carcinoma of no special type with triple-negative phenotype and a region of apocrine differentiation were determined by high-resolution microarray-based comparative genomic hybridisation and validated by fluorescence in-situ hybridisation. Morphologically distinct components were found to harbour differing genetic aberrations, with the region of apocrine differentiation demonstrating genomic gains and losses on chromosome arms 9p and 9q, respectively, not present in non-apocrine areas. The results provide additional direct evidence of intra-tumour genetic heterogeneity in breast cancer and demonstrate that morphologically distinct regions can be associated with distinct genetic aberrations.