| Japanese Journal of Clinical Oncology | Pages |
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
Introduction
Case Report
Clinical History
Histological Findings
Immunohistochemical Findings
Flow Cytometric Analysis
Immunoglobulin Heavy-chain (IgH) Gene Rearrangement Analysis by PCR
Discussion
Acknowledgments
References
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-associated lymphoid tissue (MALT) type of the urinary bladder. The patient, a 77-year-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 tissue obtained by transurethral resection (TUR) showed a dense, monomorphic atypical lymphoid (centrocyte-like) infiltrate with reactive lymph follicles in the subepithelial tissue. Monocytoid and plasmacytoid features were readily evident in a population of these cells. Lymphoepithelial lesions involving the urothelium were also noticed in some areas. These features were strongly suggestive of primary low-grade lymphoma of the MALT type. The diagnosis was confirmed by immunohistochemical and flow cytometric studies, both of which showed a clear immunoglobulin restriction to lambda light chain and also by polymerase chain reaction-based assay using a formalin-fixed paraffin-embedded TUR tissue sample, which showed a clonal Ig heavy-chain gene rearrangement. Clinical staging procedures revealed that the tumor was localized in the urinary bladder. The patient has not received chemotherapy and is alive and well with no evidence of recurrence, 3 years after TUR. This case demonstrates that these ancillary tests are worth performing for confirmation of B-cell clonality in TUR tissue samples showing dense B-lymphocytic infiltration.
Key words: malignant lymphoma - urinary bladder - immunohistochemistry - flow cytometry - polymerase chain reaction
INTRODUCTION
Primary low-grade B-cell lymphoma of the mucosa-associated lymphoid tissue (MALT) type usually involves organs with a native or acquired MALT system (1). These include the gastrointestinal tract, salivary glands, thyroid and lung. Definitive diagnosis of low-grade MALT-type lymphoma can be difficult to make even in these organs because of its morphological similarity to chronic inflammation, which often co-exists with lymphoma of this type. When it develops in rare sites, such as the urinary bladder, the tumor may be easily underdiagnosed histologically. In the case presented here, the histological diagnosis was confirmed not only by immunohistochemical stains, but also by flow cytometry and polymerase chain reaction (PCR), which gave very clear results using tissue samples obtained by transurethral resection (TUR).
CASE REPORT
Clinical History
A 77-year-old woman presented with a sense of urinary retention and painful micturition. She was diagnosed as having cystitis and was medicated with antibiotics. After there was no improvement, an intravenous pyelogram and cystoscopy revealed a wide-based submucosal mass measuring 3 cm in the left wall of the urinary bladder. TUR of the lesion was performed twice. She has not received chemotherapy and is alive and well with no evidence of recurrence, 3 years after TUR.
Histological Findings
Microscopically, the lesion consisted of dense, diffuse and vaguely nodular lymphocytic infiltration in the subepithelial tissue of the bladder (Fig. 1). Several lymphoid follicles with ill-defined borders and rather atrophic germinal centers were found throughout the lesion. Nuclei of the infiltrating lymphocytes were small to medium in size, round to oval in shape with very slight irregularity and with occasional small nucleoli. Most of these lymphocytes had plasmacytoid or abundant clear monocytoid cytoplasm (Fig. 2). A small number of Dutcher bodies were seen. Large lymphoid cells, immunoblasts, mature plasma cells and histiocytes were scattered among the atypical lymphocytes. The urothelial lining over the lesion, which showed flattening and focal squamous metaplasia, was occasionally infiltrated by lymphocytes, forming lymphoepithelial lesions (Fig. 3). In the peripheral areas of the lesion, less dense lymphocytic infiltration along with reactive lymphoid follicles were seen in the superficial zone of the mucosa, giving the impression of chronic cystitis. These morphological findings were highly suggestive of low-grade B-cell lymphoma of the MALT type. Further investigations were conducted to rule out florid inflammatory reaction and to confirm the diagnosis of malignant lymphoma.
Figure 1. Histology of the TUR tissue sample. Dense, diffuse or vaguely nodular infiltration of lymphoid cells in the subepithelial tissue is seen (left). Note the reactive lymph follicles found in the vicinity of the tumor (right) (H&E; original magnification, ×40).
Figure 2. Atypical lymphoid cells with monocytoid cytoplasm, along with scattered large lymphoid cells in some areas (H&E; original magnification, ×400).
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B
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Figure 3. (A) Atypical lymphoid aggregates present focally among the urothelial cell lining, forming lymphoepithelial lesions (H&E; original magnification, ×400). (B) Immunostain for cytokeratin to highlight lymphoepithelial lesions (immunostaining with AE1/3 antibody, Signet Laboratories, Dedham, MA; original magnification, ×400).
Immunohistochemical Findings
Formalin-fixed paraffin sections and periodate-lysine-paraformaldehyde-fixed frozen sections of TUR specimens were subjected to immunohistochemistry using the avidin-biotin complex method. The monoclonal antibodies used as a primary antibody and the immunohistochemical results are listed in Table 1. The atypical lymphoid cells were stained positive for CD19 and CD20 and negative for CD3, CD5, CD10 and CD23 (Fig. 4). They were admixed with a number of CD3-positive small T cells. In addition, there were about four times more lambda light-chain-positive plasma cells than kappa light-chain-positive cells. These results, together with the histological findings, confirmed that the lesion represented a B-cell lymphoma, compatible with low-grade lymphoma of the MALT type.
Figure 4. Atypical lymphoid cells diffusely positive for CD20 (immunostaining with L26 antibody; original magnification, ×400).
Table 1. Antibodies used and results of immunohistochemistry
| Antigen | Primary antibody | Source | Section | Result |
| CD3 | Leu4 | BD | PLP-F | - |
| CD5 | T1 | Coulter | PLP-F | - |
| CD10 | J5 | Coulter | PLP-F | - |
| CD19 | B4 | Coulter | PLP-F | + |
| CD20 | B1 | Coulter | PLP-F | + |
| CD20 | L26 | DAKO | For-P | + |
| CD21 | B2 | Coulter | PLP-F | - |
| CD23 | MHM6 | DAKO | PLP-F | - |
| CD45RO | UCHL1 | DAKO | For-P | - |
| cIg kappa | Rabbit polyclonal | DAKO | For-P | 20%* |
| cIg lambda | Rabbit polyclonal | DAKO | For-P | 80%* |
Flow Cytometric Analysis
Single-cell suspensions prepared from the TUR specimen were subjected to indirect immunofluorescence assays by flow cytometry (Spectrum-III; Ortho Diagnostic Systems, Tokyo, Japan). The results revealed a B-cell clonal population bearing CD19, CD20, HLA-DR, surface immunoglobulin G (IgG) and with the Ig light chain restricted to the lambda subtype (Table 2).
Table 2. Results of immunophenotyping by FCM
| Antigen | Result | (%)* |
| CD2 | - | (23.4) |
| CD3 | - | (23.6) |
| CD4 | - | (15.4) |
| CD5 | - | (24.0) |
| CD8 | - | (9.6) |
| CD10 | - | (7.2) |
| CD19 | + | (73.5) |
| CD20 | + | (78.5) |
| CD25 | - | (1.2) |
| CD45 | + | (99.9) |
| HLA-DR | + | (75.4) |
| sIgG | + | (74.0) |
| sIgA | - | (4.4) |
| sIgM | - | (8.7) |
| sIgD | - | (9.6) |
| sIg kappa | - | (25.4) |
| sIg lambda | + | (53.1) |
Immunoglobulin Heavy-chain (IgH) Gene Rearrangement Analysis by PCR
DNA extracted from a formalin-fixed paraffin section of TUR tissue was subjected to PCR to amplify the rearranged IgH gene. The PCR conditions and the primers used (FR2A, FR3A, LJH and VLJH) have been described previously (2). A distinct single band which was confirmed by semi-nested PCR was detected, indicating B-cell clonality in the lesion (Fig. 5).
Figure 5. A distinct band demonstrating clonal heavy-chain IgH gene rearrangement in the lesion detected by PCR using paraffin-embedded TUR tissue (semi-nested PCR). Lane 1, size marker ([phis] × 174-HincII digest); lane 2, Raji cell line (B cell lymphoma) as a positive control; lane 3, a reactive lymph node as a negative control; lane 4, the present case.
DISCUSSION
In the present case, immunohistochemical, flow cytometric and PCR-based molecular analyses together with conventional histopathological examination confirmed the diagnosis of malignant, low-grade MALT-type B-cell lymphoma of the urinary bladder.
Primary malignant lymphoma of the urinary tract is a rare disease. Although the lower urinary tract is secondarily involved in lymphoma in up to 13% of patients with systemic disease, primary malignant lymphomas of this organ system account for less than 0.2% of all extranodal lymphomas (3). In Japan, there have been only six reported cases of primary malignant lymphoma of the urinary bladder (4-7). It is also rare for low-grade lymphoma of the MALT type to occur primarily in the urinary bladder. Fourteen cases of low-grade MALT-type lymphoma of the urinary bladder have been described in the literature, including only one well-documented Japanese case (7-11). In the largest series among them, Kempton et al. (8) described six cases, five of which were diagnosed by TUR and the other by pelvic exploration.
In general, low-grade MALT-type lymphomas are believed to occur in a background of chronic active inflammation (1). It has been suggested that malignant lymphomas in the urinary bladder, especially those of the low-grade MALT type, occur in a background of preceding chronic cystitis. This seems a reasonable explanation for the fact that low-grade MALT lymphomas of the bladder are more common in women (11 women and three men in cases reported previously and also the present patient).
It is known that diagnosis of low-grade MALT-type lymphomas may often be difficult, not only clinically but also histopathologically. In the present case, we showed that TUR tissue samples could be successfully used not only for immunohistochemistry, but also for PCR-based analysis of heavy-chain IgH gene rearrangement and for flow cytometric analysis. As often performed in other tissues and organs, these ancillary studies are feasible and very effective methods to consider when histopathological examination reveals a dense lymphocytic infiltrate suggestive of, but not definitive for, low-grade B-cell lymphoma of the urinary bladder.
The reported prognosis of low-grade MALT-type lymphoma of the urinary bladder is excellent (8). In the present case, the tumor was localized in the urinary bladder and the patient has not undergone any additional therapy. She is doing well, without any evidence of recurrence 3 years after TUR. Although the number of reported cases is limited, it would be reasonable to assume that low-grade MALT-type lymphomas of the urinary bladder are clinically indolent, as are those of other organs. Optimal therapy should be further investigated by analyzing cases with a confirmed pathological diagnosis.
Acknowledgments
We are deeply grateful to Dr T. Takenaka and Mr T. Hasegawa, of the Clinical Laboratory Division, for flow cytometric analysis of the TUR tissue sample, Ms T. Shimizu for technical assistance and Mr S. Osaka for photographic work. We also thank Dr S. Hirohashi for encouragement during this work.
References
Received June 29, 1999; accepted August 31, 1999
For reprints and all correspondence: Yoshihiro Matsuno, Clinical Laboratory Division, National Cancer Center Hospital, 1-1, Tsukiji 5-chome, Chuo-ku, Tokyo 104-0045, Japan. E-mail: ymatsuno{at}ncc.go.jp
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