Differentiation of Lymphoma Presenting as Retroperitoneal Mass and Retroperitoneal Fibrosis: Evaluation with Multidetector-row Computed Tomography

Abstract

Background: Retroperitoneal fibrosis (RPF) and lymphoma presenting as retroperitoneal mass may closely resemble each other and misdiagnosis may occur. This study investigated the differential imaging features of RPF and lymphoma which presented as a retroperitoneal soft tissue using multidetector-row computed tomography (MDCT).

Methods: The 42 consecutive patients were included in this retrospective review, including 19 RPF patients (45.2%; including 13 males and 6 females; mean age: 56.7 ± 6.2 years) and 23 patients with lymphoma (54.8%; including 14 males and 9 females; mean age: 57.4 ± 12.3 years). An array of qualitative computed tomography (CT) features of lesions in 42 consecutive patients with newly diagnosed untreated RPF and lymphoma were retrospectively analyzed. The quantitative size of the lesion at the para-aortic region and attenuation in the precontrast, arterial, and portal phases were calculated in regions of interest and compared between the patients with newly diagnosed untreated RPF and with lymphoma. Receiver operating characteristic curve analysis was used to assess the potential diagnostic value of each quantitative parameter. Inter-reader concordance was also calculated.

Results: Mean ages between patients with RPF and lymphoma were not significantly different (56.7 ± 6.2 years vs. 57.4 ± 12.3 years P = 0.595). Compared to those in patients with lymphoma, homogeneous enhancement (65.2% vs. 94.7%, P = 0.027) and pelvic extension (52.2% vs. 89.5%, P = 0.017) were significantly more common while the involvement of additional nodes (78.3% vs. 5.3%, P < 0.001), suprarenal extension (60.9% vs. 15.8%, P = 0.004), and aortic displacement (43.5% vs. 5.3%, P = 0.006) were significantly less common in patients with RPF. Lesion size at the para-aorta was significantly greater in patients with lymphoma, compared with RPF patients (3.9 ± 1.2 cm vs. 1.8 ± 0.6 cm; P < 0.001). The attenuation values in three phases were not significantly different between patients with RPF and lymphoma. Inter-reader concordance for subjective features ranged from very good to excellent (range: 85.7-100.0%).

Conclusions: This study showed that MDCT can help differentiate between untreated RPF and lymphoma on the basis of qualitative CT features and lesion sizes. Differentiating RPF from lymphoma on the basis of attenuation values in the precontrast, arterial, and portal phases was difficult to accomplish.

Figure 1

(a and b) The enhanced computed tomography images of a 54-year-old male with retroperitoneal fibrosis showed homogeneous enhancement of low attenuation and relatively smooth peripheral margins of abnormal soft tissue anterior and lateral to aorta with slight anterior displacement of aorta, but the thickest part of the lesion was located in the anterior-lateral aorta (black arrows); and lesion bifurcated and followed common iliac arteries. (c and d) The enhanced computed tomography image of another 61-year-old retroperitoneal fibrosis female showed left obstructive uropathy (white arrows) and soft tissue anterior and lateral to aorta (black arrow).

Figure 2

(a and b) The enhanced computed tomography images of a 55-year-old male with lymphoma showed local peripheral enhancement and relatively smooth peripheral margins of abnormal soft tissue with anterior displacement of aorta (black arrow), noted additional lymph node at para-aorta (white arrow) and spleen lesion (star); and homogeneous enhancement abnormal soft tissue with anterior displacement of aorta (black arrow), noted the enlarged lymph nodes at the lesser omentum (white arrow), splenomegaly and spleen lesion (star). (c and d) The enhanced computed tomography image of another 60-year-old male with lymphoma showed lobulated mass of soft-tissue attenuation surrounding aorta (black arrow), in addition, abdominal fat tissue was defected between aorta and lesion, noted the enlarged retrocrural nodes (white arrow) at the level of the upper pole of the kidney.

Figure 3

Receiver operating characteristic curves for attenuation values in precontrast, arterial, and portal phases and lesion size at the para-aorta in differentiating retroperitoneal fibrosis from lymphoma.