IJU Case Reports (2023) 6, 253--256

doi: 10.1002/iju5.12599

Case Report

A case of mucosal-associated lymphoid tissue lymphoma of theurachus
Kazuma Tsuboi,1 Kensuke Bekku,2 Kohei Haisa,1 Yuta Kajihara,1 Takuji Tsugawa,1Yosuke Inoue,1 Tomoko Sako,1 Wataru Murao1 and Shin Ebara1
1Department of Urology, Hiroshima City Hiroshima Citizens Hospital, Hiroshima, and 2Department of Urology, Okayama University
Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan

Abbreviations & Acronyms
MALT = mucosa-associatedlymphoid tissue
PSA = prostate-speciﬁc
antigen
RT = radiotherapy
Correspondence: Kensuke
Bekku, M.D., Ph.D.,
Department of Urology,
Okayama University Graduate
School of Medicine, Dentistry,
and Pharmaceutical Sciences,2-5-1, Shikata-chou, Kita-ku,
Okayama 700-8558, Japan.
Email: gmd421030@s.okayamau.ac.jp
How to cite this article: Tsuboi
K, Bekku K, Haisa K et al. A
case of mucosal-associatedlymphoid tissue lymphoma ofthe urachus. IJU Case Rep.
2023; 6: 253–256.
This is an open access article
under the terms of the CreativeCommons AttributionNonCommercial-NoDerivs
License, which permits use anddistribution in any medium,provided the original work is
properly cited, the use is noncommercial and nomodiﬁcations or adaptations aremade.
Received 12 April 2023;
accepted 2 June 2023.
Online publication 14 June 2023

Introduction: Urachus carcinoma is a rare malignancy with an aggressive potential
and a poor prognosis, and evidence is limited for its diagnosis and treatment.
Case presentation: A 75-year-old man underwent fluorodeoxyglucose positronemission tomography/computed tomography for staging prostate cancer, and a mass(standardized uptake value max 9.5) was observed on the outside of the urinary bladderdome. T2-weighted magnetic resonance imaging showed the urachus and a low-intensity
tumor, which suggested a malignant tumor. We suspected urachal carcinoma andperformed total resection of the urachus and partial cystectomy. Pathologicalexamination revealed mucosa-associated lymphoid tissue lymphoma with cells positive
for CD20 and negative for CD3, CD5, and cyclin D1. After the surgery, no recurrence has
been observed for more than 2 years.
Conclusion: We encountered an extremely rare case of mucosa-associated lymphoidtissue lymphoma of the urachus. Surgical resection of the tumor provided an accurate
diagnosis and good disease control.

Key words: bladder cancer, malignant lymphoma, MALT lymphoma, urachal cancer,urachal remnant.

Keynote message
Urachal tumors are rare, which makes their preoperative diagnosis challenging. Surgical resection for localized tumors can be an effective way to accurately diagnose and treat localized
tumors with curative intent.

Introduction
The urachus is an embryological remnant that connects the umbilicus and anterior wall of thebladder. During the fourth or ﬁfth months of embryonic development, the urachus is graduallyoccluded as a ﬁbrous cord.1 However, up to 30% of the human urachus is not completelyoccluded before birth and may persist into adulthood. Urachal abnormalities are rare, andcommon complications include malignant tumors or infections. MALT lymphoma is a subtype of extranodal lymphoma that accounts for 7%–8% of B-cell lymphomas and is associated with chronic inﬂammation. The correlation between Helicobacter pylori and gastric
MALT lymphoma is well-known.2 However, MALT lymphoma rarely affects the genitourinary organ.3 Here, we report an extremely rare case of MALT lymphoma arising in theurachus.

Case presentation
A 75-year-old man was referred to our department with an elevated serum PSA level(8.14 ng/mL). He had no medical history related to the urachus. Transrectal prostate needle
biopsy revealed prostate cancer, with a pathological type of adenocarcinoma and a Gleason
score of 8. Fluorine-18 ﬂuorodeoxyglucose positron emission tomography/computed© 2023 The Authors. IJU Case Reports published by John Wiley & Sons Australia, Ltd on behalf of Japanese Urological Association.

253

tomography was used for staging, which revealed a 30-mm
mass protruding from the dome of the bladder to the central lower abdominal wall (standardized uptake value max
9.5; Fig. 1). T2-weighted magnetic resonance imaging
revealed a low-intensity mass in the dome of the bladderalong the urachus (Fig. 2), which was suspected to be amalignant tumor. The periphery was well-deﬁned andunlikely to be invasive to the surrounding tissues. Additionally, there were no abnormalities that were suspected to bemetastatic lesions of prostate or urachal cancer. Cystoscopy
revealed elevated mucosa in the dome of the bladder(Fig. 3). We diagnosed the patient with localized urachal
cancer and decided to perform total resection of the urachus
and partial cystectomy. Simultaneously, we diagnosed localized prostate cancer and initiated hormonal therapy. The
operating time was 76 min, and minimal bleeding occurred
during surgery. The tumor did not adhere to the surrounding tissues and showed good mobility. However, en blocFig. 3 As the circle points out, cystoscopy shows elevated mucosa on theposterior wall of the bladder.

Fig. 1 As the arrows point out, Fluorine-18 fluorodeoxyglucose positronemission tomography/computed tomography shows a mass with a hot spot
(standardized uptake value max 9.5) protruding from the dome of the bladder to the central lower abdominal wall.

resection of the bladder wall was performed because thepossibility of a malignant tumor could not be excluded during surgery. Microscopic ﬁndings showed ﬁbrous tissue thatwas considered as the urachus and diffuse proliferation oflymphocytes (Fig. 4a). The pathological examination, whichused immunohistochemical staining, showed that the cells
were positive for CD20 but negative for CD3, CD5, andcyclin D1 (Fig. 4b). The lesion was found to exist in theextranodal marginal zone, without any high-grade features.
B cells showed diffuse proliferation without any follicle formation, ruling out the possibility of mantle lymphoma or
follicular lymphoma. Based on these ﬁndings, the diagnosis
of MALT lymphoma was made. The patient has not experienced any postoperative complications or evidence of recurrence for more than 2 years. The serum PSA level wasmaintained below the detectable level under hormonal
therapy.

Discussion

Fig. 2 As the circle points out, T2-weighted magnetic resonance imaging
shows a mass with a low-intensity area from the dome of the bladder along
the urachus.

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Urachal carcinomas are rare malignancies, accounting for
approximately 1.0% of urinary bladder cancer.4 Therefore,
the evidence regarding diagnosis and treatment is sparse, andclinical features, typical imaging ﬁndings, and effective tumor
markers remain unknown.5 Diagnostic criteria include thelocation of the tumor in the dome or anterior wall of thebladder, growth of the tumor in the bladder wall, absence ofatypical cystitis or glandularis beyond the dome/anterior wall,
absence of urothelial carcinoma in the bladder, and absenceof another origin of adenocarcinoma.6 Although the patient
was diagnosed with prostate adenocarcinoma, we excluded
the possibility of metastasis of prostate cancer because his
initial PSA level was low, and the urachus is an uncommonsite for solitary metastasis of prostate cancer.
Urachal carcinomas typically have aggressive potential5;
therefore, rapid diagnosis and treatment are necessary.

© 2023 The Authors. IJU Case Reports published by John Wiley & Sons Australia, Ltd on behalf of Japanese Urological Association.

2577171x, 2023, 4, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/iju5.12599 by Okayama University, Wiley Online Library on [19/08/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License

K TSUBOI ET AL.

system. The optimal management of MALT lymphoma has
not been clearly established9; therefore, several treatment
options, such as RT, surgery, chemotherapy alone, and a
combination of these modalities, are chosen according to theindividual case.9 RT could be a good treatment option, as it
is highly sensitive to radiation. However, surgical resection
is used as the initial therapy for nongastric MALT lymphoma when the tumor is localized or not amenable to RT.9
Patients with nongastric MALT lymphoma have a favorable
outcome with a 5-year overall survival rate of 86%.2 However, MALT lymphoma is a heterogeneous disease and has
the potential to progress to a high-grade histologic subtype,such as diffuse large B-cell lymphoma. Regular monitoring
and follow-up are important for detecting changes in the disease over time.10
The preoperative pathological diagnosis could have
impacted the treatment strategy for MALT lymphoma andprostate cancer in this case. However, surgical resection of
the urachal tumor was a minimally invasive and effective
approach, providing an accurate pathological diagnosis andcurative treatment. Although evidence is limited, total resection of the tumor and the urachal ligament, umbilicus, andbladder dome is the mainstay in the management of localized
urachal carcinoma.7 When the surgery is technically feasible,
the resection of a localized urachal tumor suspected ofmalignancy is effective.

Conclusion

Fig. 4 (1) On microscopic findings, the circle points out a lumen structure
considered to be the urachus (magnification 9100). (2) Pathological findingsof immunohistochemistry staining show cells that are positive for CD20 andnegative for CD3, CD5, and cyclin D1 (magnification 920).

However, detecting tumors localized in the urachus can bechallenging, and patients may not experience objective symptoms or abnormalities in urine tests or cytology. Additionally,transurethral tissue sampling may result in bladder wall perforation when tumors do not grow inside the bladder cavity.
Percutaneous needle biopsy carries the risk of puncturing
adjacent organs, such as the small intestine. Furthermore,
there are no speciﬁc pathological criteria for diagnosing urachal carcinomas, although adenocarcinoma is the typical
pathology.7 Therefore, under clinical suspicion of localized
urachal carcinoma, tumor removal is acceptable, even without
pathological conﬁrmation. The previous report showed that
two rare tumors arose in the urachus, namely a desmoid anda solitary ﬁbrous tumor.8 The preoperative diagnosis for both
tumors was urachal carcinoma, and frozen sections of theintraoperative biopsy revealed no malignancy. The reportconcluded that an accurate preoperative diagnosis was difﬁcult.8
To the best of our knowledge, this is the ﬁrst reported
case of urachal MALT lymphoma. MALT lymphoma is asubtype of extranodal lymphoma associated with a chronic
immune response to bacteria, viruses, or the autoimmune

Here, we present a case of MALT lymphoma that originatedin the urachus. Due to their infrequency, preoperative diagnosis of urachal tumors is challenging. In cases of localized
diseases, surgical excision of the tumor can be beneﬁcial
for both pathological conﬁrmation and effective diseasecontrol.

Author contributions
Kazuma Tsuboi: Writing – original draft. Kensuke Bekku:
Writing – review and editing. Kohei Haisa: Writing – reviewand editing. Yuta Kajihara: Writing – review and editing.
Takuji Tsugawa: Writing – review and editing. Yosuke
Inoue: Writing – review and editing. Wataru Murao: Writing– review and editing. Tomoko Sako: Writing – review andediting. Shin Ebara: Writing – review and editing.

Conflict of interest
The authors declare no conﬂict of interest.

Approval of the research protocol by
an Institutional Review Board
Not applicable.

Informed consent
Not applicable.

© 2023 The Authors. IJU Case Reports published by John Wiley & Sons Australia, Ltd on behalf of Japanese Urological Association.

255

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MALT of the urachus

Registry and Registration No. of thestudy/trial
Not applicable.

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© 2023 The Authors. IJU Case Reports published by John Wiley & Sons Australia, Ltd on behalf of Japanese Urological Association.

2577171x, 2023, 4, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/iju5.12599 by Okayama University, Wiley Online Library on [19/08/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License

K TSUBOI ET AL.