Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) involving the ureter is particularly uncommon, and histological transformation to diffuse large B- cell lymphoma (DLBCL) further complicates diagnosis and management. We report a case of a female patient presenting with obstructive uropathy caused by long-segment ureteral wall thickening radiologically suggestive of urothelial carcinoma. Endoscopic evaluation and biopsies were inconclusive, leading to nephroureterectomy. Histopathological examination unexpectedly revealed MALT lymphoma with areas of transformation to DLBCL. This case highlights a rare diagnostic pitfall and emphasizes the importance of considering lymphoma in the differential diagnosis of atypical ureteral strictures.
Bernardo et al. (2026) studied this question.