Intramural sarcoma of the carotid artery with adventitial inflammation and fibrosis resembling 'inflammatory aneurysm'.

A rare case is described of an intramural sarcoma of the right common carotid artery coexisting with adventitial inflammation and fibrosis, resembling 'inflammatory aneurysm', which was resected from a 33-year-old Japanese woman who had presented with a pulsatile mass on the right side of the anterior neck. Grossly, the wall of the carotid artery showed an intimal tear with dissection of the media filled with thrombus. A grayish area, abutting directly onto the dissected space and involving the media and inner adventitia, was composed of alpha-smooth muscle actin-positive and desmin-negative polygonal and spindle cells with large blunt-ended nuclei and coarse granular chromatin arranged into a well-organized interlacing bundle pattern. This portion was thus considered to represent leiomyosarcoma. White to yellow-tan fibrotic tissue present in the adventitial area consisted of extensive lamellar fibrosis with scattered foci of lymphoplasmacytic aggregates and obliterated arteries, and lacked atypical spindle and polygonal cells. These changes accorded with the histopathological findings hitherto described in cases of 'inflammatory aneurysm', which is known to almost exclusively involve the abdominal aorta. We consider this case unique in that the leiomyosarcoma involved an artery other than the aorta, with an 'inflammatory aneurysm'-like reaction in the same site. The possible relationship between these two conditions is discussed.