Vascular tumors of the breast are extremely rare, and the majority are malignant. In this report, the presentation of a diffuse, benign, cystic, vascular tumor that histologically was angiomatosis of the breast is described. The clinical presentation, magnetic resonance imaging (MRI) appearance, and histologic features of this rare lesion are reviewed. This case is of particular interest because the tumor recurred during pregnancy and underwent massive enlargement despite negative hormone receptor values. Angiomatosis is prone to local recurrence, so complete excision with histologically negative margins is the treatment of choice.