Breast cancer affects women at relatively high frequency (1). We mined published microarray datasets (2, 3) to determine in an unbiased fashion and at the level of the transcriptome genes most differentially expressed in the primary tumors of women with breast cancer. We found significant differential expression of the gene encoding SWI/SNF related, matrix associated, actin dependent regulator of chromatin, subfamily a, member 4, SMARCA4, when comparing primary tumors of the breast to the tissue of origin, the normal breast: in women aged 70 and higher, and in women aged 45 and younger. SMARCA4 mRNA was present at significantly higher quantities in tumors of the breast as compared to normal breast tissue. Analysis of human survival data revealed that expression of SMARCA4 in primary tumors of the breast was correlated with recurrence-free survival in human breast cancer. SMARCA4 may be of relevance to initiation, maintenance or progression of cancers of the female breast.