Retroperitoneal Mass: Lymphoma as Differential Diagnosis to Retroperitoneal Fibrosis: Case Report

The etiology of solid retroperitoneal mass may be autoimmune or neoplastic and should be investigated by imaging and histology. The spectrum of differential diagnoses includes retroperitoneal fibrosis and retroperitoneal tumors. As treatment for these entities differs substantially, early and accurate diagnosis is essential. We present a case of a 54-year-old woman admitted to our hospital with stroke-like symptoms. Suspecting vasculitis, magnetic resonance imaging of the head and abdomen was performed, which revealed circular enhancement of the internal carotid artery as well as retroperitoneal and periaortic masses. In light of the radiographic findings, an autoimmune process, such as retroperitoneal fibrosis, was hypothesized. Steroid treatment was initiated but did not lead to significant remission. Re-evaluation of the mass with fine-needle aspiration did not show malignant cells while diagnostic surgery and histological assessment revealed neoplastic lymphoproliferation. The final diagnosis was a non-Hodgkin B-cell lymphoma. Chemo- and immunotherapy were initiated. Follow-up abdominal computed tomography revealed significant remission of the retroperitoneal mass. Initially, the retroperitoneal mass was highly suspicious for RF. While imaging can be useful, obtaining histology should always be considered when there is an uncertain clinical presentation. Without histology, we would have missed a non-Hodgkin B-cell lymphoma in this case. Minimally invasive techniques such as fine-needle aspiration may be practical but can give false-negative results.