Diffuse dermal angiomatosis (DDA) is a rare reactive angioproliferation in the skin and considered to be a subtype in the group of cutaneous reactive angiomatoses. DDA is clinically characterized by livedoid patches and plaques with tender ulceration. Its histologic features are a reactive diffuse proliferation of bland endothelial cells and pericytes within the dermis, forming small capillary vessels. Previously described cases of DDA most commonly involved the limbs and were associated with a wide spectrum of predisposing comorbidities, especially advanced atherosclerotic vascular disease and arteriovenous fistula. However, several cases of DDA of the breast (DDAB) have been reported in recent years. In this study we present 2 additional patients with DDAB and review all 36 cases of DDAB published in the literature. We describe the clinical and histopathologic characteristics, hypothesized pathogenetic mechanisms, and predisposing conditions of this rare skin disorder and discuss treatment options. The breast is a more commonly involved site of DDA than previously believed. DDAB typically occurs in middle-aged women and is associated with macromastia, overweight or obesity, and probably smoking. Predisposing comorbid conditions differ from those of DDA involving other parts of the body, making DDAB a unique clinicopathologic entity in the spectrum of cutaneous reactive angiomatoses. Currently there is no consensus on the best therapeutic approach. Isotretinoin and other medical therapies have been used with limited success. Breast reduction surgery appears to be a viable treatment option for DDAB in women with macromastia and might provide definitive healing.