Lymphedema (LE) following treatment for breast cancer is the most common form of secondary LE in the industrialized world. It occurs in 20% to 87% of patients following treatment for breast cancer and results in significant disability. At the present time, the definitive phenotypic, genotypic and epigenotypic predictors that place patients at highest risk for the development of LE are not known. Therefore, the specific aims of this study, in a sample of patients following treatment for breast cancer, are to: determine genetic predictors of LE using a candidate gene approach and evaluate for epigenetic changes, as measured by DNA methylation and subsequent gene expression, in candidate genes associated with the diagnosis of LE. The secondary aims of this study are to: evaluate for latent classes of women with distinct phenotypic predictors of LE; and evaluate for differences in symptoms, functional status, and QOL outcomes between women with and without LE and among the latent classes with LE. The results of this study will provide new information on the underlying mechanisms for LE and allow for the development and testing of novel approaches to prevent or reduce the negative effects of LE.