Renal lymphoma: demonstration by MR imaging.

OBJECTIVE: The objective of this study was to demonstrate the spectrum of appearances of renal lymphoma using current MR techniques including gadolinium enhancement.

MATERIALS AND METHODS: Twelve patients with renal lymphoma were examined by MR imaging on a 1.5-T scanner. MR examinations included T2-weighted, breath-hold T1-weighted spoiled gradient-echo, and T1-weighted fat-suppressed spin-echo imaging before and after gadolinium administration. Tumor morphology, signal intensity, and enhancement features were evaluated.

RESULTS: Three types of renal involvement were observed: large paraaortic retroperitoneal masses with extension into the renal hilum, the subcapsular space, or both (nine patients); unilateral diffuse infiltration of the renal parenchyma (one patient); and focal rounded intraparenchymal masses (two patients). Untreated lymphoma (10 patients) was slightly hypointense relative to the renal cortex on T1-weighted images and was heterogenous and slightly hypointense or isointense on T2-weighted images. Enhancement of lymphomatous tissue was mildly heterogenous and was minimal on early images after gadolinium enhancement and remained minimal on late contrast-enhanced images in most tumor masses. No central necrosis of tumor was identified, and no renal vein thrombus was present. Five patients with lymphoma that presented as a large paraaortic mass showed diminished renal cortical perfusion of the involved kidney. All of these patients also had tumor extension into the renal hilum.

CONCLUSION: Three types of renal involvement with lymphoma were observed. The most common appearance was a large retroperitoneal mass that invaded the kidney. Tumors had low to intermediate signal intensity on T1- and T2-weighted images and had diffuse heterogenous enhancement that was less than that of renal parenchyma.