Which histologic findings are characteristics of angiosarcoma of the scalp?

Updated: Jan 03, 2020
  • Author: Jonathan S Zager, MD, FACS; Chief Editor: Gregory Gary Caputy, MD, PhD, FICS  more...
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Histologically, early lesions may show benign, capillary, hemangiomalike structures. This pattern, however, is deceiving, because angiosarcoma usually has an aggressive course. Microscopically, angiosarcoma often shows extensive involvement of the dermis, with poorly differentiated tumors also invading deep structures such as fascia and subcutis. The histopathologic features of angiosarcoma are diverse. The 3 histologic patterns are vascular channels, sheets of cells, and cells of undifferentiated morphologic features. In some lesions, more than one pattern may be present.

Low-grade angiosarcoma is a well-differentiated lesion that retains some of the functional and morphologic properties of normal vascular endothelium. Well-differentiated lesions form distinct vascular channels, although these are often irregular in shape and size. Unlike benign hemangiomas, well-differentiated angiosarcoma forms vascular channels that create its own tissue planes as it dissects through the dermal collagen. In addition, unlike normal epithelium, angiosarcoma is characterized by cells with larger and more chromatic nuclei, with cells often piling up along the lumina, creating papillations. Low-grade tumors have infrequent mitoses.

In poorly differentiated (high-grade) tumors, sheets of pleomorphic cells may resemble a carcinoma. The vascular anastomosing channels typically observed in angiosarcoma are lined by atypical endothelium that can be either a single row of cells or multiple layers thick. In highly cellular tumors, the neoplastic process causes such close approximation of cells within vascular spaces that the tumor may appear solid. Higher-grade lesions have areas of hemorrhage, disordered architecture, and large cells with hyperchromatic, pleomorphic nuclei. Cells often display prominent mitotic activity. Occasionally, tumors may have well-differentiated areas, but often they are composed exclusively of poorly differentiated areas.

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