Radiology: Volume 260: Number 2-August 2011
Patricia Sims Poole, MD Eric Y. Chang, MD Cynthia S. Santillan, MD
History: A 24-year-old woman presented with intermittent dull abdominal pain of 2 months duration. She reported no association with food and no alleviating factors. She denied any recent travel. She did not report any fever, flushing, nausea, vomiting, diarrhea, constipation, melena, or he-matochezia. She had no relevant medical history; specifically, there was no history of human immunodeficiency virus infection. Physical examination findings and all laboratory values, including complete blood count and basic metabolic panel, were normal. She subsequently underwent computed tomography (CT) of the abdomen and pelvis followed by magnetic resonance (MR) imaging of the abdomen and pelvis for further evaluation.
Imaging Findings: We first performed contrast material-enhanced CT through the abdomen and pelvis. This revealed a solid hyperattenu-ating retroperitoneal mass with a thin surrounding capsule and slightly enlarged left paraaortic lymph nodes (Fig 1). The rest of the abdominal and pelvic organs were normal. Follow-up MR imaging was performed 4 days later. The retroperitoneal mass was homogeneously isointense to muscle on Tl-weighted images (Fig 2). The mass did not have signal intensity changes between in-phase and opposed-phase images consistent with a lack of lipids. On T2-weighted images, the mass was homogeneous, with signal intensity slightly greater than that of muscle (Fig 3). Dynamic postcontrast imaging revealed avid early enhancement of the retroperitoneal mass (Fig 4a), with central hypointensity relative to the surrounding capsule and adjacent retroperitoneal lymph nodes on subsequent delayed images (Fig 4b). Higher-spatial-resolution 9-minute delayed contrast-enhanced images showed fine internal septations (Fig 5).
Discussion: Differential diagnosis for these imaging findings included infection, inflammatory conditions, lymphoma, mesenchymal tu-mors (including sarcoma, solitary fibrous tumor, leiomyoma, gastrointestinal stro-mal tumors, and hemangiopericytoma), carcinoid, and paraganglioma (extraad-renal pheochromocytoma). The clinical presentation combined with the imaging findings contributed to the exclusion of many entities within the differential diagnosis. The lack of constitutional symptoms with normal laboratory values made diagnosis of an infectious disease highly unlikely. Lymphoma was included within the differential diagnosis. In patients with un-treated lymphoma, all abnormal lymph nodes typically have similar contrast en-hancement. However, the imaging find¬ings showed a single dominant lesion with contrast kinetics that differed from those of the multiple surrounding lymph nodes, making lymphoma a less likely diagnosis. Contrast enhancement, signal in-tensity, and attenuation were fairly ho-mogeneous within the dominant mass
