Revisiting and demystifying primary and secondary renal lymphoma: A series of two cases.

Lymphoma is a multisystem malignancy with diverse imaging manifestations across various organs. Multiple studies have documented its extra nodal spread to the genitourinary system, particularly the kidneys-second only to the hematopoietic and reticuloendothelial systems. Renal involvement is usually secondary, termed secondary renal lymphoma (SRL). In contrast, primary renal lymphoma (PRL), which arises in the absence of systemic disease, is exceedingly rare, accounting for approximately 1% of all extra nodal lymphoma cases with its rarity attributed to the paucity of lymphoid tissue in the renal parenchyma. Although PRL and SRL differ in origin and prevalence, they often share overlapping clinical and radiologic features, making accurate diagnosis crucial for appropriate management. This report presents 2 cases-one of PRL and 1 of SRL-highlighting their clinical presentation, imaging findings, diagnostic challenges, and treatment strategies, supported by a comprehensive literature review.