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INTRODUCTION

The nomenclature of vascular lesions is at best confusing and in some instances is entirely incoherent. Thus, the same terminology may be used to describe unrelated clinical entities, and there are examples of a variety of different terms being applied to a single condition. To illustrate this point, “cavernous hemangioma” has been used to designate both a venous malformation (VM) and a hemangioma of infancy. In fact, the latter 2 entities are characterized by completely different clinical features, natural histories, and managements. Because the pathogenesis of many lesions is still poorly understood, many classifications have been proposed. However, no single classification to date is entirely satisfactory.1-4

This chapter adheres to the classification scheme recommended by the International Society for the Study of Vascular Anomalies (ISSVA), which is based on the distinction between proliferative lesions (vascular tumors and reactive proliferative lesions) and vascular malformations (Table 31-1). Vascular malformations may be further classified as to the type or caliber of predominant vascular channel present (eg, capillaries, veins, arteries, lymphatics, or glomus vessels). With this conceptual basis, this chapter will discuss (1) benign vascular tumors (ie, different types of hemangiomas) and proliferative vascular lesions of reactive or indeterminate nature, (2) vascular tumors of low grade or borderline malignancy, (3) malignant vascular tumors, and (4) vascular malformations and acquired nonproliferative vascular lesions. In addition, the chapter attempts to clarify the nomenclature and to maintain a balanced perspective in discussing each entity without trying to resolve all of the controversial issues of nomenclature and pathogenesis.

TABLE 31-1SSVA Classification Scheme for Vascular Anomalies

Vascular tumors are endothelial tumors that are derived from either blood vessel endothelial cells (BEC) or lymphatic vessel endothelial cells (LEC), while perivascular tumors—including angioleiomyoma, symplastic hemangioma, myopericytoma, and glomus tumor—are composed of smooth muscle cells and their derivatives (ie, pericytes, myopericytes, and glomus cells). The first routinely applied endothelial antibodies, Ulex europaeus agglutinin 1 lectin (UEA-1) and Factor VIIIRA (von Willebrand factor), have been replaced by more reliable, sensitive, and user-friendly endothelial antibodies: ERG (nuclear signal), CD31, Fli1 (nuclear signal), and CD34 (HPCA1/my10). Remarkably, all these antibodies show wide and characteristic cross-reactivities that may provoke diagnostic pitfalls.5 ERG, apart from vascular neoplasms, also decorates Ewing sarcoma (5% to 10%), prostatic adenocarcinoma (50%), and acute myeloid leukemia (small subset). CD31 cross-reacts with a wide range of inflammatory and neoplastic histiocytic proliferations. Fli1 shows expression in Ewing sarcoma, lymphoblastic lymphomas, and a subset of mesenchymal tumors, carcinomas, and melanomas. CD34 is a widely used marker of various fibroblastic tumors.

Highly specific markers for small subsets of BECs are GLUT1, which stains the ...

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