Breast edema is defined as a mammographic pattern of skin thickening, increased parenchymal density, and interstitial marking. It can be caused by benign or malignant diseases, as a result of a tumor in the dermal lymphatics of the breast, lymphatic congestion caused by breast, lymphatic drainage obstruction, or by congestive heart failure. Here we describe several conditions, that cause unilateral breast edema with the aim of familiarizing radiologists with these disease entities.