Nam Kyung Lee, MD , Suk Kim, MD , Gwang Ha Kim, MD , Tae Yong Jeon, MD , Dae Hwan Kim, MD , Ho Jin Jang, MD , Do Youn Park, MD
Although the vast majority of gastrointestinal (GI) masses are epi-thelial neoplasms, a variety of subepithelial masses are infrequently encountered during endoscopic or radiologic examination. A subepi¬thelial mass, which was previously called a submucosal mass, is de¬fined as a mass covered with normal-appearing mucosa, whether the underlying process is intramural or extramural in origin. At contrast material-enhanced computed tomography (CT), hypervascular sub¬epithelial masses are usually detected more easily than isoattenuating or hypovascular masses. Entities that appear as intramural hypervas¬cular subepithelial lesions include neuroendocrine tumors, GI stromal tumor, glomus tumor, hemangioma, angiosarcoma, Kaposi sarcoma, nerve sheath tumors, hypervascular metastases, heterotopic tissues, and vascular structures. Entities that appear as extramural hypervas¬cular subepithelial lesions include Castleman disease, solitary fibrous tumor, inflammatory myofibroblastic tumor, and actinomycosis. Some rare gastric cancers resemble subepithelial tumors. In comparison with endoscopic ultrasonography, CT is of limited value in differen¬tiating the layers of the GI wall and determining the origin of mass lesions. However, recent advances in multidetector CT with multi¬planar reformation allow one to determine whether a GI mass is of epithelial, intramural subepithelial, or extramural subepithelial origin. Furthermore, the full extent of tumors can be delineated, and local invasion and distant metastases can be identified. Familiarity with the characteristic CT appearances of hypervascular subepithelial masses of the GI tract will help radiologists make a more confident diagnosis.