Fig. 1. RNA expression profiling separates postpartum breast cancer (PPBC) from nulliparous breast cancer (NPBC).

RNA seq, performed on RNA obtained from FFPE specimens of primary ER+ breast cancer from patients 45 years of age or younger, reveals parity effect. Clustering analysis derived from RNA expression profiles of biologically independent samples of nulliparous breast cancer (NPBC, blue, n = 7) and postpartum breast cancer (PPBC, black, n = 9). a Euclidean hierarchical clustering of the 14,830 genes determined to be expressed above background. b Euclidean hierarchical clustering based upon 364 differentially expressed genes between PPBC and NPBC determined by DESeq2 with an FDR < 0.1. c STRING database clustering analysis⁵⁴ of 185 upregulated PPBC genes generates two distinct biological clusters of statistical significance (adj = adjusted. p values adjusted according to Benjamini–Hochberg for multiple comparisons).