1) The study analyzed DNA methylation patterns between young (<45 years old) and older (>=45 years old) women with breast cancer using data from The Cancer Genome Atlas. 2) Machine learning identified 17 differentially methylated sites between the two groups, including hypomethylation of the ITPR3 promoter and hypermethylation of the ARID3A gene in young women. 3) Differential methylation of these genes, particularly ITPR3 which stimulates breast cancer cell proliferation, may help explain the increased aggressiveness of breast cancer in young women. Further investigation of these genes is warranted.