Renal lymphoma: radiologic-pathologic correlation of 21 cases.

The radiologic findings in 21 cases of renal lymphoma were correlated with the gross and microscopic pathologic findings. The gross morphology and consequent radiographic images depend upon the mechanism of renal involvement (hematogenous or direct extension); the pattern of intrarenal growth (interstitial or expansile); the size, number, and distribution of lesions; and the presence of extension beyond the kidney. Initially, the lymphoma grows between nephrons that may continue to function and, because this interstitial proliferation preserves gross morphology, radiographic detection may be difficult. With continued growth, the scaffolding along which the tumor infiltrates is destroyed, growth becomes expansile, and the lymphomatous mass resembles other renal neoplasms that enlarge by appositional growth. Continued growth and coalescence of small foci result in progressive parenchymal replacement and, rarely, in destruction of the entire kidney. Perinephric extension with subsequent vascular and ureteral encasement is common.