A 60-year-old woman with neurofibromatosis type 1 presented with a nonpainful swelling in the left laterocervical region that had suddenly arisen after mild exertion the previous evening. Computed tomography with and without contrast enhancement revealed a rupture of the wall of the left internal jugular vein, with a diffuse subcutaneous hematoma. Postoperative histopathologic examination reported diffuse proliferation of plexiform neurofibromatous tissue within the vessel wall.