Intravascular fasciitis of the forearm vein: a case report with immunohistochemical characterization.

Intravascular fasciitis is a very unusual variant of nodular fasciitis. A unique case of this lesion occurring in the proximal portion of the superficial vein of the forearm in an otherwise healthy 26-year-old man is reported. The intravascular polypoid lesion grew longitudinally along the vascular lumen, was loosely attached to the intimal layer, and was partly anchored beyond the internal elastic lamina into the medial smooth muscle layer. However, extravascular involvement was absent. The histological features were identical to those observed in ordinary cellular nodular fasciitis. Because of its myofibroblastic phenotype exhibited by highly proliferative spindle cells, certain intimomedial myofibroblasts are thought to be the indigenous source of this unique fibroproliferative lesion. Unless the diagnosis of intravascular fasciitis is considered and appropriate differential markers examined, it may be confused with other intravascular lesions, such as intravascular leiomyoma, intravenous pyogenic granuloma, organized thrombus and, even, fibromuscular dysplasia if it arises in the arteries. A simple excision is considered curable. Even so, two recurrent cases have been documented to date.