Primary mucosa‐associated lymphoid tissue lymphoma of the urinary bladder

To the Editor,

Lymphoma of the urinary bladder (LUB) is rare, and < 100 cases have been reported [1]. Primary LUB is an extremely rare disease, constituting < 1% of all bladder neoplasms and comprising 0.2% of the extranodal lymphomas [2]. Mucosa‐associated lymphoid tissue (MALT) lymphoma is the most common subtype of lymphomas in the urinary bladder. Here, we describe a case of primary bladder MALT lymphoma.

A 76‐year‐old female suffered from recurrent urinary tract infection for 1 year. A computed tomography scan showed an eccentric thick wall of the urinary bladder and right hydronephrosis. Cystoscopy revealed erythematous mucosa with a yellowish wide‐based submucosal mass near the right ureteral orifice. Transurethral biopsy for the bladder mass was done. The hematoxylin and eosin stain of the biopsy specimen showed urothelial epithelium infiltrated by submucosal proliferation small to medium‐sized lymphoid cells with vesicular nuclei. The immunohistochemical studies of these tumor cells were diffuse positive for CD20 and Bcl‐2, and negative for CD3, CD10, and cytokeratin (Fig. 1). A bone marrow biopsy revealed normal findings. Based on the clinical data, pathohistological findings, and immunohistochemical profile, the diagnosis of primary bladder MALT lymphoma stage IE (Ann Arbor classification) was established. The patient received radiotherapy, and remission of tumor was found on follow‐up computed tomography 3 months after radiotherapy.

Figure 1.

A 76‐year‐old female. (A) Noncontrast abdominal computed tomography (CT) shows right eccentric thickening of the bladder wall. (B) Cystoscopy reveals erythematous mucosa with a yellowish wide‐based submucosal mass near the right ureteral orifice. (C) Excision specimens reveal submucosal infiltration of small to medium‐sized lymphoid cells in a vaguely nodular fashion (hematoxylin and eosin stain; original magnification, ×100). Immunohistochemically, tumor cells were diffuse positive for (D) CD20 and (E) Bcl‐2 (original magnification, ×400).

Primary bladder MALT lymphoma is primarily a localized disease, which tends to spread along mucosal tracts [[2], [3]]. It is frequently associated with chronic cystitis and autoimmune disease, and typically affects adults who are > 60 years of age, and 75% are female [[1], [2], [3]]. MALT lymphoma is clinically indolent and slow to disseminate.

The radiological investigations of LUB show as submucosal masses: solitary masses in 70% of cases, multiple masses in 20% of cases, and diffuse bladder wall thickening in 10% of cases [1]. Transurethral resection or biopsy is often required to establish a diagnosis of LUB. Histopathologically, MALT lymphomas exhibit sheets of low‐grade, uniform cells, which surround and separate—but do not destroy—muscle fascicles [1]. Immunochemically, MALT lymphoma is positively stained for CD20 and CD19. It is negatively stained for CD5, CD10, and CD11c [1]. Although rearrangements of the bcl‐2 gene are rarely detected in MALT lymphoma, diffuse expression of bcl‐2 has been found in MALT lymphoma except for large cell transformation cases [4].

The most effective therapeutic procedure for primary bladder MALT lymphoma is still under debate. Complete endoscopic resection of the bladder tumor may not be required as radiotherapy and chemotherapy are useful and effective in the treatment of LUB [[1], [5]]. Chemotherapy with rituximab plus cyclophosphamide, doxorubicin/mitoxantrone, vincristine, and prednisone (R‐CHOP/R‐CNOP) has been used in patients with relapsed MALT lymphoma [1]. Primary bladder MALT lymphoma has an excellent prognosis with virtually no tumor‐related mortality [5].