Vascular tumors: an update with emphasis on the diagnosis of angiosarcoma and borderline vascular neoplasms.

It is clear from this selective review that the category of vascular tumors remains a great source of interest and diagnostic challenge because of its complex and heterogeneous constituents. Accurate diagnosis of the relatively infrequent angiosarcomas, with particular emphasis on avoiding overdiagnosis, remains crucial since the clinical outcome is generally very poor, especially when compared with the relatively innocent angiomatous lesions often mistaken for it. Equally, it is important to avoid confusing either spindle cell hemangioendothelioma or tufted angioma with Kaposi's sarcoma inasmuch as the connotations of the latter (especially in young patients) are considerable. Finally, the concept of borderline malignancy in vascular tumors is evolving and is still poorly defined. However, the number of tumors often placed in this category is expanding, and the indolent or unpredictable biologic behavior of these tumors will continue to pose problems and questions for pathologist and clinician alike.