Lymphoid neoplasms of the urinary tract and male genital organs: a clinicopathological study of 40 cases.

Lymphoid neoplasms of the urinary tract and male genital organs are relatively rare, comprising less than 5% of all primary extranodal lymphomas; only a handful of small case series and isolated case reports have been published describing their predominant sites and subtypes. We identified 40 patients with lymphoid neoplasms of the urinary tract and male genital organs. Hematoxylin and eosin slides and immunohistochemical stains were reviewed, and follow-up data were also obtained. Twenty-six of 40 cases (65%) were primary genitourinary lymphomas. Mean age at diagnosis was 56 years (range 4-86 years). Among renal, bladder, and ureter lymphomas, a male predominance was noted (1.6:1). The subtypes of the lymphoid neoplasms observed were diffuse large B-cell lymphoma (17 cases, 43%); Burkitt lymphoma, extranodal marginal zone lymphoma, SLL/CLL, and follicular lymphoma (4 cases, or 10% each); B-cell ALL (2 cases, 5%); B-cell lymphoma, unclassifiable, with features intermediate between diffuse large B-cell lymphoma and Burkitt lymphoma, mantle cell lymphoma, plasmacytoma, polymorphic post-transplant lymphoproliferative disorder, and peripheral T-cell lymphoma NOS (1 case, or 2.5% each). In most cases, the genitourinary tract was the site of initial presentation. Genitourinary tract lymphomas most commonly occurred in the kidney. B-cell non-Hodgkin's lymphomas predominated, with diffuse large B-cell lymphoma being the most common subtype in the entire group. Extranodal marginal zone lymphoma was seen only in the kidney, rather than the bladder, where it is typically thought to be more common. Although this study confirms the predominance of diffuse large B-cell lymphoma in extranodal sites, the findings also highlight the variety of lymphomas that may occur in the genitourinary tract. This diversity of subtypes affirms the importance of fully characterizing lymphomas by immunohistochemistry and other modalities, which are indispensable for accurate diagnosis.