CT diagnosis of extra-gastrointestinal stromal tumors

Objective: To analyze the CT features of extra-gastrointestinal stromal tumors (EGIST). Methods: CT of 14 patients with histologically confirmed EGIST was analyzed retrospectively. Results: The tumors were located in the mesentery (7), retroperitoneum (5) and omentum (2) with tumor size ranging from 3 to 200 mm. Multiple masses were found in 3 patients. CT showed small round or oval nodules with clear delineation from the adjacent bowel in 4 patients and irregular or round masses adherent to surrounding intestine in 10 patients. One tumor mass showed homogeneous CT density of 31 HU with contrast enhancement to 50-60 HU. The remaining tumors were heterogeneous with CT densities of 30-42 HU with heterogeneous contrast enhancement to 50-90 HU and non-enhancing central necrosis. Punctate calcifications were noted in one solid tumor and small annular calcifications were found in the periphery of one tumor mass. There were liver metastasis (4), lymph node metastasis (4), and local invasion (1). Conclusions: EGIST are histologically identical to GIST. Because of the different locations and growth patterns, EGIST have variable imaging features and clinical prognosis. (authors)