Periureteral Marginal Zone Lymphoma Resulting in Hydronephrosis and Flank Pain in the Absence of Disseminated Disease: Case Report of Two Patients Presenting with Rare But Important Differential.

Background: Extrinsic compression of the ureter can result from multiple different malignancies, typically in the presence of known or disseminated disease. Rarely, hydroureteronephrosis and flank pain can occur as the presenting sign and symptom of lymphoma. In this study, we present two cases of primary ureteral obstruction in patients without a prior diagnosis of lymphoma and without bulky retroperitoneal lymphadenopathy. Case Presentation: Case #1 was a healthy 58-year-old man who presented with acute left flank pain. He was found to have left hydroureteronephrosis secondary to a proximal periureteral mass. Diagnostic ureteroscopy demonstrated this to be an extrinsic compression on the ureter and preoperative imaging was negative aside from one enlarged periaortic node. Laparoscopic ureterolysis and biopsy were remarkable for periureteral dystrophic tissue concerning for lymphoma. Case #2 was a 47-year-old woman with a solitary kidney secondary to prior left nephrectomy who presented with hydronephrosis of her solitary kidney and acute kidney injury. Retrograde pyelogram showed high-grade obstruction at the junction of the mid- and distal ureter. Periureteral thickening was noted, but no definitive masses were seen on cross-sectional imaging. Robotic ureterolysis showed dense fibrosis around the ureter. Pathology report from Cases #1 and #2 were both remarkable for marginal zone lymphoma and both patients received bendamustine and rixuximab with resolution of ureteral obstruction and their lymphoma. Conclusion: Ureteral compression as the primary presentation of periureteral lymphoma is a rare but important etiology of extrinsic malignant ureteral obstruction. These cases emphasize that malignant obstruction can occur even in the absence of disseminated disease.