Angiosarcoma, radiation-associated angiosarcoma, and atypical vascular lesion.

Angiosarcoma, one of the least common sarcomas, has become increasingly important because of its association with radiation therapy, especially for breast cancer. Most are sporadic, presenting as cutaneous tumors in the scalp/face of elderly patients. However, angiosarcoma has a wide anatomic distribution including soft tissue, visceral organ, and osseous locations. Predisposing conditions include environmental exposures to chemical or radioactive sources. Radiation-associated angiosarcoma typically presents as a cutaneous tumor several years posttherapy. The latency for radiation-associated mammary angiosarcoma is relatively short, sometimes less than 3 years. Atypical vascular lesion refers to a small, usually lymphatic-type vascular proliferation in radiated skin. Although most atypical vascular lesions pursue a benign course, they recur and very rarely progress to angiosarcoma. Distinguishing this lesion from well-differentiated angiosarcoma in a biopsy can be challenging, especially because areas indistinguishable from atypical vascular lesion are found adjacent to angiosarcoma. Recently, vascular-type atypical vascular lesion, which resembles hemangioma, has been described, thus expanding the definition of this entity.