Intravascularly disseminated angiosarcoma: true neoplastic angioendotheliomatosis? Report of two cases.

Although vascular invasion is common in many malignant tumors, disseminated intravascular anaplastic neoplasms with occult primary tumor are rare occurrences. Intravascular malignant lymphoma, also called angiotropic lymphoma, is a rare variant of large cell lymphoma predominantly involving vessels in multiple organs, and usually without significant nodal involvement. Although initially misinterpreted as an endothelial neoplasm-angioendotheliomatosis-immunohistochemical studies subsequently proved it to represent a peculiar form of malignant lymphoma. In this report, we describe two patients with extensive intravascular dissemination of angiosarcoma initially without clinically obvious primary tumor. These may be interpreted as examples of true angioendotheliomatosis. In each case the immunohistochemical studies ruled out the most common intravascular malignant neoplasms. The diagnosis of intravascular angiosarcoma was confirmed by the immunoreactivity of the tumor cells to several markers of endothelial lineage in both cases. Thus, angiosarcoma may present with intravascular dissemination and occult primary tumor and closely resemble metastatic carcinoma, melanoma, or angiotropic lymphoma. Immunohistochemical studies are crucial in ruling out these possibilities and in confirming the endothelial origin of the neoplastic cells.