Lymphoma involving the kidneys alone without evidence of disease elsewhere is a rare entity accounting for less than 1% of all renal masses. A disease typically treated with chemotherapy, Primary Renal Lymphoma (PRL) is classically of the non-Hodgkins subtype. While metastatic renal involvement is not uncommon in disseminated lymphoma secondary to contiguous retroperitoneal or systemic hematogenous spread, primary lymphoma of the kidney, an organ typically devoid of lymphoid tissue, is exceedingly rare. For this reason, primary lymphoma of the kidney is often not considered in the work up of renal masses and this may place the patient at risk of inappropriate management, delays to diagnosis and unnecessary morbidity. Here, we present a rare case of primary renal b-cell lymphoma diagnosed on histopathology following robotic nephroureterectomy.

PubMed, Embase, Ovid MEDLINE, SCOPUS, CINAHL and Cochrane Review databases were searched for individual cases or case series of PRL. A total of 24 studies were identified. Only one study described haematuria as a presenting symptom of PRL. No studies identified within our search described PRL with involvement of the renal pelvis. Lastly, only three studies were identified with patients proceeding to nephrectomy and in no studies did patients undergo nephroureterectomy.

An 82-year-old male presented to hospital with haematuria. Past medical history included impaired renal function, ischaemic heart disease, type 2 diabetes, hypertension, and dyslipidaemia. CT intravenous pyelogram identified a filling defect within the right renal pelvis. Urine cytology was inconclusive. Inpatient pyeloscopy was organised revealing a tumour within the renal pelvis. This was not biopsied at the time. The patient was then medically optimised and underwent an uncomplicated right robotic nephroureterectomy. While the surgery was uncomplicated, the patient suffered a type two myocardial infarction delaying their post operative recovery. Despite the presumed diagnosis, histology revealed a diffuse large B-Cell lymphoma extending through the renal capsule into perirenal fat, renal vein and renal pelvis. Haematology were consulted and chemotherapy was offered, however, given significant frailty, the patient declined active treatment, instead opting for palliation and the voluntary assisted dying pathway.

Our report describes a rare case of Primary Renal Lymphoma mistaken for a urothelial primary. Unfortunately, this may have resulted in surgery and morbidity thay may have been avoidable. We highlight the clinical similarities between upper tract TCC and PRL and the high index of suspicion a urologist must show toward alternative diagnosis when investigating upper tract lesions. Additionally, we encourage urologists to consider biopsies of indeterminate lesions, particularly amongst the frail population prior to consideration of surgery.