Benign vascular proliferations in irradiated skin

Several types of cutaneous vascular proliferations have been described in areas of irradiated skin, including both benign lesions, such as benign lymphangiomatous papules, atypical vascular lesions, or benign lymphangioendothelioma, and malignant neoplasms such as high-grade angiosarcomas. This report describes the clinicopathologic features of 15 cases of different types of benign cutaneous vascular proliferations arisen within irradiated skin. All patients were female ranging in age from 33 to 72 years, and they had received postoperative external radiotherapy for treatment of breast carcinoma (14 cases) or ovarian carcinoma (one case). In those cases in which the latency interval period between radiotherapy and the development of the vascular lesion was known from the clinical records, the latency interval period elapsed between radiotherapy and diagnosis of the vascular lesion ranged from 3 to 20 years. The most common clinical presentation of the cutaneous lesions consisted of papules, small vesicles, or erythematous plaques on the irradiated field. Histopathologically, most lesions consisted of irregular dilated vascular spaces, with a branching and anastomosing pattern, thin walls, and lymphatic appearance involving the superficial dermis. A discontinuous single layer of endothelial cells with flattened nuclei lined these vascular channels, and numerous small stromal papillary formations also lined by endothelial cells projected into the lumina of the dilated lymphatic vessels. These cases were classified as benign lymphangiomatous papules or plaques. Two cases showed different histopathologic findings because they consisted of poorly circumscribed and focally infiltrating irregular jagged vascular spaces involving the entire dermis and lined by inconspicuous endothelial cells. In some areas these irregular slit-like vascular spaces dissected collagen bundles of the dermis. These cases were classified as atypical vascular proliferations mimicking benign lymphangioendothelioma or patch-stage Kaposi's sarcoma. All cases showed similar immunohistochemical findings and the endothelial cells lining the vascular spaces expressed immunoreactivity for CD31, but they stained only focally positive for CD34 or were negative for this marker. Immunohistochemical investigations for alpha-smooth muscle actin failed to demonstrate a complete peripheral ring of actin-positive pericytes in most of the neoformed vascular structures. This immunohistochemical profile also supported the lymphatic nature of these vascular proliferations developed in irradiated skin. Although some of these lesions may mimic histopathologically patch-stage Kaposi's sarcoma or well-differentiated angiosarcoma, the follow-up of the patients of this series demonstrated that the vascular proliferations arisen in irradiated skin invariably showed a benign biologic behavior.