We report the clinicopathologic study of 32 cases of atypical vascular lesions (AVLs) after surgery and radiation of the breast, which were referred to us in consultation over a 17-year period. The patients, all women, ranged in age from 41 to 95 years (mean 61 y). The lesions developed within the radiation field from 1 to 12 years (median 6.0 y) after therapy. They occurred as one (n=18) or more (n=10) flesh-colored papules or erythematous patches/plaques ranging in size from 1 to 60 mm (mean 8.0 mm, median 4.0 mm). Tumors could be divided into 2 histologic types: a lymphatic type (LT) (n=22) and a vascular type (VT) (n=10). LT AVLs consisted predominantly of thin-walled, variably anastomosing lymphatic vessels that were usually confined to the superficial dermis but occasionally extended into the deep dermis and even subcutis. The VT (n=10) typically consisted of small, irregularly dispersed, often blood-filled, pericyte-invested, capillary-sized vessels involving the superficial or deep dermis. VTs were often associated with extravasated erythrocytes, hemosiderin, and a surrounding minor LT component. In 4 cases, endothelial atypia, consisting of nuclear and nucleolar enlargement, was noted. Follow-up of 21 patients with LT AVLs (1 to 106 mo; mean 47 mo) disclosed recurrence/additional lesions in 6, all of whom had additional surgery. Of the 21 patients, 17 are alive without disease, 1 is alive with disease, 1 died of breast carcinoma, 1 died of unknown causes, and 1 showed progressive histologic changes in the AVLs over a period of 5 years resulting in a well-differentiated angiosarcoma. Follow-up in 8 patients with VT AVL (2 to 181 mo; mean 40 mo) disclosed that 6 were alive and well, but 2 of the 4 patients whose lesions displayed endothelial atypia had additional complications. One patient underwent a mastectomy that revealed extensive residual AVL and the second developed a high-grade angiosarcoma after 14 months. We conclude that AVLs encompass a wider spectrum of changes than previously appreciated, ranging from superficial lymphatic proliferations to more complex lymphatic and capillary vascular lesions. There seems to be an association of AVL with angiosarcoma that differs depending on the histologic features, with the VT AVLs having the higher risk. In the 2 patients who developed angiosarcoma, morphologic evidence suggested AVLs to be a precursor rather than simply a risk factor. Future outcome and management studies should take into account these differences.