Molecular characterization of male breast cancer by standardized quantitative RT-PCR analysis: First large genomic study of 347 male breast cancers compared to 82,434 female breast cancers

549 Background: Because male breast cancer (BC) is rare, there is little known about the disease and treatment is extrapolated from female BC. Newer molecular technologies have not been used to profile male BC. We report here a study of quantitative gene expression by gender status in tumor specimens submitted for Recurrence Score testing. Methods: All estrogen receptor positive tumor specimens successfully examined in the Genomic Health laboratory from June 2004 through December 2008 were included. Quantitative expression for each gene was measured by the 21 gene oncotype DX assay on a scale from 0 to 15 (relative to reference genes), where a one unit increment is associated with a 2-fold change in expression. Results: There were 347 male and 82,434 female BCs. The males were older (mean age 63.8 vs 57.4 yrs). Standard histopathology was similar, although slightly more male BCs were ductal (83% vs 78%). Like female BC, there was a wide variation in gene expression in male BC. The distribution of RS in ma...