MR Imaging of Soft-Tissue Vascular Lesions: Pathologic Correlation

common causes of soft tissue masses. Because of the absence of unifying concepts and accurate definitions, significant confusion remains as to appropriate classification. The term “hemangioma”has been used as a generic word to describe a variety of vascular lesions, and in the past has been used to describe a combination of the hemangioma of infancy and venous malformation with confusing radiologic findings (1, 2). In the biological classification system proposed by Mulliken et al. (2), based on cellular turnover, histology, natural history, and physical findings, congenital vascular lesions are usually separated into the hemangioma of infancy and vascular malformation (capillary, lymphatic, venous, arterial, or combined). This classification has been useful clinically because unlike venous malformation, the hemangioma of infancy can undergo involution, and has recently been adopted for interventional radiology (1, 2, 4). There are, however, also various the other masses of vascular origin, including angioleiomyoma, angiolipoma, hemangiopericytoma, angiosarcoma and soft tissue hematoma. Others may mimic a nonvascular soft tissue mass or congenital vascular lesions and should be differentiated (5). MR imaging can be used to distinguish slow-flow lesions (venous and lymphatic malformations) from highflow lesions (hemangioma of infancy, arteriovenous malformation and fistula) on the basis of their spin-echo MR signal characteristics. Slowand high-flow vascular lesions are distinguished primarily on the basis of their T2-weighted MR imaging findings: high signal intensity is seen in slow-flow lesions, and flow voids in high-flow lesions (3). MR imaging can also represent features of the nonvascular components or static tissues of vascular lesions in which fibrofatty components, smooth muscle, thrombosed vessels, phleboliths and muscle atrophy are present (3, 6). Because surgical cure is rare in arteriovenous malformation or fistula, and in a hemangioma of infancy spontaneous involution is possible, pathologic specimen of J Korean Radiol Soc 2001;45:69-77