Updated project metadata. About 15-20% of all breast cancers are triple negative breast cancers, which are often highly aggressive. We performed global quantitative phosphotyrosine profiling of a large panel of triple negative breast cancer cell lines using high resolution Fourier transform mass spectrometry. Our study identified 1,903 tyrosine-phosphorylated peptides derived from 969 proteins. Heterogeneous activation of tyrosine kinases was observed in triple negative breast cancer derived cell lines.