A Large Renal Mass: Dilemmas With Unusual Features on Imaging.

A 50-year-old man presented with palpable abdominal mass which on CT revealed a large tumor replacing the entire right kidney, filling the right hemi-abdomen and travelling down the ureter into the bladder with retroperitoneal lymphadenopathy. Urine cytology and metastatic workup were negative. Ultrasound guided renal biopsy revealed diffuse large B cell lymphoma (DLBCL) and the patient was started on combination chemotherapy. Primary urinary tract lymphomas comprise <1% of all renal tumors and primary urinary tract DLBCL lymphomas carry a worse prognosis than nodal DLBCL. Biopsy of very large renal masses without distant metastasis or hematuria may significantly change management.