[Mesenchymal tumors of the pancreas: computed tomography patterns]

To report the CT patterns of pancreatic mesenchymal lesions and to investigate the capabilities and limitations of this technique in terms of characterization.

We selected the CT examinations of 23 patients from all CT examinations of the pancreas performed from 1986 to 1998. The patients were 10 to 85 years old and all lesions but two (1 lipoma and 1 lymphoma) had pathologic confirmation. Two lymphangiomas, 2 lipomas, 4 Schwannomas (SCH), 1 plexiform neurofibroma, 1 cystic teratoma, 1 pancreatoblastoma, 9 non-Hodgkin's lymphomas (NHL), 1 undifferentiated sarcoma and 2 leiomyosarcomas were diagnosed.

Lipomas had typically homogeneous negative HU values, and NHL a homogeneous hypodense pattern with mild contrast enhancement, with no necrosis or calcifications in both diffuse and nodular forms; SCH had variable appearance, with water/slightly negative HU numbers or highly enhanced patterns with a central necrotic core depending on the main Antoni A or B histology. Lymphangiomas appeared as complex cysts, with thin and regular or calcified walls and intracystic septa, while the plexiform neurofibroma had near-water homogeneous density with mild contrast enhancement and an infiltrating growth pattern. Our teratoma had multiple calcifications, mucinous and lipid components. The pancreatoblastoma, sarcomas, and leiomyosarcomas exhibited no specific findings.

In selected cases, CT can provide virtually diagnostic information (lipoma and teratoma), or at least highly suggestive findings (NHL, plexiform neurofibroma, lymphangioma). Moreover, knowledge of the variable morphostructural patterns of mesenchymal histotypes (SCH, sarcoma etc.) permits to include them in the differential diagnosis of pancreatic masses.