Intimal sarcoma (IS) is defined as a malignant tumor arising in the tunica intima of large blood vessels. In systemic circulation, the majority of IS develop in the aorta, where close to three fourths of published cases lack specific differentiation and are called undifferentiated intimal sarcomas (UIS). The remaining cases are intima-associated sarcomas of recognized types, also called differentiated intimal sarcomas (DIS). In this report, we further characterize UIS, including its immunohistochemical profile and results of comparative genomic hybridization. A total of 14 cases of UIS were collected from 17 medical institutions, including slides, blocks, electron photomicrographs, clinical abstracts, and reports of surgical pathology specimens and autopsies. The patients, 7 women and 7 men, were 41 to 85 years of age (median, 65.6 years). Twelve tumors arose from the aorta, one from the left external iliac and femoral arteries, and one in a large systemic vein (the venous tumor was included due to histologic similarity with the arterial lesions). Tumors ranged from 1 cm to over 10 cm in diameter. Histopathology was that of a largely necrotic, poorly differentiated epithelioid and pleomorphic malignant neoplasm relating to the tunica intima. Usually there was only a thin layer of viable tumor cells overlying a large thrombus. All tumors stained at least focally with the endothelial markers CD31 and Fli-1; however, there was otherwise considerable variability in immunophenotype. The distinctive histopathologic appearance of the primary luminal lesion was lost whenever tumor invaded outside the vessel wall (into adventitia and beyond) or in metastatic sites. Such extravascular tumors assumed a variety of patterns reminiscent of undifferentiated pleomorphic sarcoma (UPS; in older literature also known as pleomorphic malignant fibrous histiocytoma, MFH) or other distinct types of sarcomas, including osteosarcoma, angiosarcoma, and rhabdomyosarcoma. The results of comparative genomic hybridization were nonspecific. Eleven patients died of the disease, in an average of 11 months after diagnosis. Three patients are still alive and free of disease at 4, 16, and 27 years. UIS of large systemic vessels represents a distinct clinical entity where intraluminal sarcoma presents with thrombosis and occlusion of large vessels. It is associated with a highly characteristic, although not entirely specific, histology and immunohistochemical phenotype. The histogenesis of UIS is not certain; however, it seems that the cell of origin must leave the confines of the vessel wall to show altered morphology. Although there are rare long-term survivors, UIS behaves as a fully malignant neoplasm that is almost uniformly associated with metastases and tumor-related death.
