BACKGROUND: Cutaneous vascular proliferations that occur in the field of prior radiotherapy include angiosarcoma and small, cutaneous lesions with a pseudosarcomatous pattern that previously were reported as atypical vascular lesions or benign lymphangiomatous papules. METHODS: The objective of this study was to investigate the clinicopathologic features and outcomes of 56 radiation-induced vascular proliferations that occurred in 36 patients who received previous treatment for breast carcinoma. Data from all patients were retrieved from the files of the French Sarcoma Group. Immunostaining with D2.40 antibody was performed in 24 lesions. RESULTS: All patients (median age, 52 years) had received external radiotherapy. Small papules developed within the field of prior radiotherapy (median latency interval, 66 months). Microscopically, the lesions were relatively well circumscribed, and they were located mostly in the superficial/middermis. They were composed of dilated or irregular-jagged vascular channels that were lined by a single layer of bland endothelial cells, and they demonstrated either a predominately lymphangioendothelioma-like or lymphangioma/lymphangioma circumscriptum-like growth pattern. Micropapillary tufts were common findings. Ten lesions showed additional cytologic and/or architectural atypia. Twenty of 24 lesions showed D2.40 positivity. Follow-up information was available for 31 patients (median follow-up, 48 months): Five women developed new cutaneous lesions, and 1 woman had spontaneous regression of her lesions. None of the patients developed cutaneous angiosarcoma. Five patients were lost to follow-up. CONCLUSIONS: Although vascular proliferations in irradiated skin may mimic angiosarcoma morphologically, the large majority of these lesions showed a benign clinical outcome. Despite relatively limited follow-up, the current results indicate the benign nature of these vascular proliferations