Primary triple-negative breast cancers represent approximately 16% of all breast cancers and, based on expression prof ling, are a heterogeneous tumor type. We present an integrated analysis of somatic aberrations (nonsynonymous coding mutations, copy number aberrations, fusions and translocations) in 104 of these cancers, using multiple views of the genome and transcriptome. We show that the basal subtype of triple-negative breast cancer contains more somatic aberrations of all types than the nonbasal subtype, as well as enrichment for mutations in certain pathways; some pathways exhibit an unprecedented somatic mutation enrichment pattern for low-frequency, single gene mutations, but in many related gene family members. We found that triple-negative breast cancers of both subtypes are heterogeneous at the time of diagnosis, with a wide variation in the content and type of somatic aberration among tumors. However, individual tumors can be grouped by the degree and extent of somatic aberration in ten distinct pathways, suggesting a future route for genomic phenotyping of these cancers.