Triple negative breast cancer (TNBC) refers to tumours where the estrogen receptor (ER) and progesterone receptor are negative. In addition, HER2 neu is not over-expressed. Hence the term, “triple negative”. TNBC can be associated with a poor prognosis. Clinically it appears that there are two types of TNBC; one (about 40%) that are particularly aggressive and tends to recur within 12-24 months of first presentation. The other type is more indolent and tends to behave more like ER positive tumours. The hypothesis of the study was that by examining the genes of TNBC it would be possible to see different patterns of gene changes between the aggressive type of TNBC versus the more indolent type. In the study TNBC cases were identified in the Ontario Tumour Bank which contains frozen samples of cancers from across Ontario. These samples then underwent gene sequencing which is a complex test that identifies mutations (changes) in the genes. The test results from TNBC patients who had developed recurrence were compared with the results from patients who had not developed recurrent cancer. No difference in gene sequencing results were detected between groups. One explanation for the negative results was that not enough sample were studied.