Primary low-grade lymphoma of mucosa-associated lymphoid tissue of the urinary bladder: a case report with special reference to the use of ancillary diagnostic studies

We report a case of primary low-grade B-cell lymphoma of the mucosa-associa ted lymphoid tissue (MALT) type of the urinary bladder. The patient, a 77-y ear-old woman, presented with a sense of urinary retention. An intravenous pyelogram and cystoscopy revealed a wide-based submucosal mass measuring 3 cm in the left wall of the urinary bladder, Histological findings of the ti ssue obtained by transurethral resection (TUR) showed a dense, monomorphic atypical lymphoid (centrocyte-like) infiltrate with reactive lymph follicle s in the subepithelial tissue. Monocytoid and plasmacytoid features were re adily evident in a population of these cells, Lymphoepithelial lesions invo lving the urothelium were also noticed in some areas. These features were s trongly suggestive of primary low-grade lymphoma of the MALT type. The diag nosis was confirmed by immunohistochemical and flow cytometric studies, bot h of which showed a clear immunoglobulin restriction to lambda light chain and also by polymerase chain reaction-based assay using a formalin-fixed pa raffin-embedded TUR tissue sample, which showed a clonal Ig heavy-chain gen e rearrangement, Clinical staging procedures revealed that the tumor was lo calized in the urinary bladder. The patient has not received chemotherapy a nd is alive and well with no evidence of recurrence, 3 years after TUR. Thi s case demonstrates that these ancillary tests are worth performing for con firmation of B-cell clonality in TUR tissue samples showing dense B-lymphoc ytic infiltration.