4. Discussion: Epidemiology and Diagnostic Considerations

Genitourinary tract lymphomas account for a minority of extranodal lymphomas; detailed syntheses of reported ureteral lymphomas emphasize their rarity and the diagnostic challenge posed by nonspecific imaging and endoscopic appearances [1, 4, 5]. Several reports highlight the spectrum of presentation from distal ureteral strictures to pelviureteric junction obstruction, with patients presenting with flank pain, hydronephrosis, or signs of renal impairment [2, 4]. Although the case discussed refers to an isolated malignancy involving the ureter, secondary lymphoma has been noted to infiltrate the renal system [6]. In striking similarity to prior reports, the patient also presented with abdominal pain, hydronephrosis, and symptoms of postrenal obstruction that were initially puzzling on ureteric imaging, mimicking urothelial carcinoma and renal colic [7, 8].

Urothelial carcinoma often presents with hematuria, while ureteral lymphoma has been described to present without constitutional symptoms and hematuria [8]. Imaging often fails to support the diagnosis of ureteral lymphoma because it mimics urothelial carcinoma, being described as ureteral wall thickening that is concentric and homogenous in enhancement [8]. Thus, with radiological imaging modalities, findings are often nonspecific to ureteral lymphoma [7].

The differential for ureteral obstruction also included IgG4‐related retroperitoneal fibrosis, which has been shown to cause ureteral encasement on imaging and postrenal obstructive uropathy [9]. However, this disease is more likely to affect elderly males, IgG4/IgG would be above 40%, and retroperitoneal lesions would be present [9]. In addition, symptoms associated with symptomatic effect on the great vessels, kidneys, and psoas muscle would likely be present, but not all of such features were seen in the current patient [9]. A closely related idiopathic cause of retroperitoneal fibrosis was also unlikely in the patient because the disease more often affects young males, and fibrosis would be more likely on biopsy [9]. Furthermore, endometriosis with ureteral involvement was determined to be unlikely due to the lack of endometriosis at other pelvic sites like the bladder (the most common location of genitourinary migration) and gynecologic symptoms like chronic pelvic pain, dysmenorrhea, dyspareunia, and cyclical pain [10].

Likewise, diagnostic challenges in the patient′s case were similar to the existing literature, often with no definitive preoperative diagnosis prior to surgical excision [7, 8]. Histopathological and immunohistochemical analysis after surgical resection is frequently necessary for a diagnosis [7]. The existing literature suggests that lymphoma can affect various regions of the genitourinary tract and pose significant diagnostic and clinical challenges. Distinguishing primary ureteral lymphoma from secondary involvement or regional nodal disease can be nuanced; historical criteria and proposed frameworks emphasize the predominance of extranodal presentation in isolated extranodal involvement, though definitive categorization may be difficult in the setting of multifocal lymphoid disease [1, 2, 4]. Although prior case reports have noted ureteral lymphoma, primarily with reports of being mainly diffuse large B‐cell or with transformation from marginal zone lymphoma, the present case expands the literature on being a marginal zone lymphoma causing a focal ureteral obstruction without renal or bladder involvement [6–8]. Ureteral lymphoma should be on the differential in cases of obstructive uropathy, especially when endoscopic evaluation, imaging modalities, or biopsy are not able to support a leading diagnosis [7, 8]. The case is limited due to its low generalizability and lack of follow‐up.