Urachal mucinous tumors are rare neoplasms with behaviour that can range from relatively benign to malignancy that can spread distantly or throughout the peritoneum as pseudomyxoma peritonei or peritoneal carcinomatosis. Here we describe a unique case of urachal mucinous cystic tumor of low malignant potential confined to an intact cyst at the dome of the urinary bladder, without rupture or peritoneal spread. The urachal mucinous tumor was an incidental finding on a staging CT scan performed for sigmoid colon adenocarcinoma. We believe that this case illustrates a potential diagnostic pitfall which could have prognostic and therapeutic implications. Due to the intestinal phenotype of these neoplasms, a urachal tumor of low malignant potential could be mistaken for metastatic spread from a colonic adenocarcinoma in the rare situation such as this case, where the two neoplasms occur concurrently.
Urachal neoplasms are thought to arise from neoplastic transformation of remnant urachal tissue left from incomplete regression of the urachus in fetal development [
Classification of epithelial neoplasms of urachal origin with emphasis on the cystic mucinous neoplasms, modified from Paner et al., 2016, & Amin et al., 2014 [
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(i) Adenoma |
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(ii) Cystic mucinous neoplasms: |
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(a) Mucinous cystadenoma (cystic tumor with a single layer of mucinous columnar epithelium, with no atypia) |
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(b) Mucinous cystic tumor of low malignant potential (cystic tumor with areas of epithelial proliferation, including papillary formation |
and low-grade atypia/dysplasia) |
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(c) Mucinous cystic tumor of low malignant potential with intraepithelial carcinoma (cystic tumor with significant epithelial |
stratification and unequivocal malignant cytological features and often with stroma-poor papillae and cribriform pattern) |
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(d) Mucinous cystadenocarcinoma with microinvasion (stromal invasion <2mm and comprising <5% of the tumor) |
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(e) Frankly invasive mucinous cystadenocarcinoma (stromal invasion that is more extensive than 2mm and 5%) |
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(iii) Non-cystic adenocarcinoma |
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(i) Urothelial neoplasm |
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(ii) Squamous cell neoplasm |
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(iii) Neuroendocrine neoplasm |
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(iv) Mixed-type neoplasm |
NOS: not otherwise specified.
Summary of literature review of urachal mucinous tumors.
Primary Study Author | Year | N | Age | Sex | PMP | Size (cm) | Diagnosis | Concurrent neoplasms | Presentation/symptoms | Extent of Surgical Treatment |
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Agrawal [ | 2014 | 1 | 50 | M | Yes | 8 | low grade mucinous urachal neoplasm | No | Abdominal pain | Cystic mass resection, partial cystectomy, extended parietal peritonectomy |
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Amin [ | 2014 | 24 | 24-80 (mean 47) | 9 M | Unk | 0.8-13 (mean 5) | 4 mucinous cystadenomas, 20 Mucinous cystic tumors of low malignant potential | Not mentioned, 1 case had a concurrent sigmoid colectomy performed | Hematuria, umbilical mass, incidental finding, suprapubic mass, mucusuria, abdominal pain, bladder dome nodule, urgency, obstruction, umbilical discharge, pelvic mass, midline cystic mass | Cystic mass resection, partial cystectomy, umbilectomy |
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Carr [ | 2001 | 1 | 72 | M | No | 4 | Urachal mucinous tumor of uncertain malignant potential | No | Hematuria (microscopic), nocturia | Cystic mass resection, partial cystectomy |
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Chahal [ | 2015 | 1 | 37 | M | No | 4 | Mucinous cystic tumor of low malignant potential (MCTLMP) | Yes - stage pT2, non-stem germ cell tumor | Incidental finding | Partial cystectomy, left hydrocelectomy |
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Choi [ | 2012 | 1 | 29 | F | No | 5.5 | Urachal mucinous tumor of uncertain malignant potential | No | Right flank pain | Cystic mass resection, partial cystectomy |
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Fahed [ | 2012 | 1 | 66 | M | No | 9 | Adenocarcinoma in situ | No | Lower abdominal pain and groin pain | Cystic mass resection, partial cystectomy |
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Gupta [ | 2014 | 1 | 15 | F | No | 4.5 | Low grade mucinous neoplasm with uncertain malignant potential | No | Lower abdominal pain | Cystic mass resection |
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Hubens [ | 1995 | 1 | 40 | M | No | 8 | Urachal adenoma | No | Incidental finding | Cystic mass resection, cholecystectomy |
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Hull [ | 1994 | 1 | 32 | M | No | 14 | Urachal Cystadenoma | No | Incidental finding | Cystic mass resection |
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Nozaki [ | 2011 | 1 | 37 | M | Yes | 5 | Mucinous borderline tumor of low malignant potential | No | Abdominal pain | Cystic mass resection, extensive peritonectomy |
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Pasternak [ | 2014 | 1 | 28 | F | No | 8 | Mucinous urachal neoplasm of low malignant potential | No | Incidental finding | Cystic mass resection, partial cystectomy, umbilectomy, omentectomy, bilateral pelvic lymphadenectomy |
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Paul [ | 1998 | 1 | 68 | M | No | 3 | Stage 0 mucinous adenocarcinoma in situ of the urachus | No | Hematuria, mucusuria | Cystic mass resection, partial cystectomy |
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Prakash [ | 2014 | 1 | 58 | M | No | 10 | Complex mucinous cystadenoma of undetermined malignant potential of the urachus | No | Lower abdominal pain | Cystic mass resection |
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Saha [ | 2011 | 1 | 60 | F | No | 3 | Mucinous cystadenoma | No | Urinary frequency | Cystic mass resection |
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Schell [ | 2009 | 1 | 70 | F | No | 15.5 | Complex mucinous cystadenoma of undetermined malignant potential of the urachus | No | Lower abdominal mass | Cystic mass resection, partial cystectomy |
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Shinohara [ | 2006 | 1 | 54 | M | Yes | 9 | Mucinous cystic tumour with low malignant potential | No | Found incidentally during left inguinal hernia repair | Cystic mass resection, partial cystectomy, intraperitoneal lavage |
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Stenhouse [ | 2003 | 1 | 54 | M | Yes | 14 | Mucinous neoplasm of uncertain malignant potential | No | Abdominal pain, rectal bleeding | Not available |
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Wang [ | 2016 | 1 | 54 | M | No | 4 | Urachal mucinous cystic tumor of low malignant potential | No | Hip pain | Cystic mass resection, partial cystectomy, umbilectomy |
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Wu [ | 2017 | 1 | 41 | M | No | 3 | Urachal cystadenoma with unknown malignant potential | No | Lower abdominal swelling and pain | Cystic mass resection, partial cystectomy |
PMP: pseudomyxoma peritonei; UNK: unknown.
Care was provided at a tertiary care teaching hospital and the patient provided written consent for a review of medical records and for publication of a case report, in accordance with institutional policy. Data regarding clinical history, diagnostic imaging, and pathology were collected retrospectively.
The patient, a 67-year-old male, underwent a colonoscopy after a positive Fecal Immunochemical Test result in the province’s colon cancer screening program. On review of systems, the patient reported a change in bowel habits, specifically cramping and a sense of urgency. His past medical history was unremarkable apart from hypertension and hyperlipidemia. Colonoscopy revealed a stricturing malignancy in the distal sigmoid colon. Biopsies were diagnostic of colonic adenocarcinoma. A CT scan of the chest, abdomen, and pelvis demonstrated a 6.5 cm segment of circumferential wall thickening in the sigmoid colon, 20 cm from the anal verge. The CT scan also identified an incidental, 6.9 x 4.8 cm rim calcified cystic lesion arising from the dome of the urinary bladder, suspected to represent a bladder diverticulum or a urachal cyst (CT scan illustrated in Figure
Sagittal image from contrast enhanced CT demonstrating a 6.9 cm rim calcified cyst (see Arrow) arising from the dome of the urinary bladder (labelled “B”) corresponding to a urachal cystic tumor of low malignant potential. Immediately posterior to this is the 6.5 cm sigmoid colon adenocarcinoma (labelled
On gross examination, the cyst from the dome of the bladder measured 9.0 x 5.5 x 5.0 cm. It was unilocular and thin walled (0.1-0.6 cm thick), partially calcified, and lacked any grossly identifiable papillary projections or solid component. The cyst content was mucin. On H&E microscopy, the epithelial lining consisted of a single layer of cuboidal to columnar epithelial cells with an intestinal phenotype, including scattered goblet cells (illustrated in Figure
(a) Cyst wall showing fibromuscular wall and surface epithelial lining (20X Magnification). (b) Cyst epithelial lining with nuclear pseudostratification (H&E 200X Magnification). (c) Cyst with an area of simple papillary architecture (H&E 100X Magnification). (d) Cyst showing epithelial expression of CDX2 by immunohistochemistry (100X Magnification).
The sigmoid colon contained a 5.5 cm circumferential mass. Histologically, the tumor was a moderately differentiated invasive adenocarcinoma, not otherwise specified (illustrated in Figure
(a) Invasive colonic adenocarcinoma (20X Magnification). (b) Invasive colonic adenocarcinoma (200X Magnification). (c) Colonic adenocarcinoma showing epithelial expression of CDX2 (200X Magnification).
There were no postoperative complications. The patient did not receive systemic chemotherapy or radiation therapy following surgery. Nine months after surgery, he presented to the emergency department with a productive cough and a chest X-ray identified two left upper lobe lung nodules, 7mm and 11mm in diameter, suspicious for metastases. The two lung lesions were removed by video assisted thoracoscopic surgery. Histologically, the lung lesions were invasive adenocarcinoma with no mucinous component. The morphology was identical to the sigmoid colon adenocarcinoma. Six months after resection of the lung metastases (18 months after presentation), the patient had no further evidence of metastasis or local recurrence.
The urachus is a vestigial remnant derived from the embryonic tissue connecting the allantois to the urinary bladder [
Forty-two cases of urachal mucinous cystic neoplasms have been described in the literature, in eighteen case reports and a case series of 24 patients, summarized in Table
The most significant potential pitfall in this case would have been a pathologist interpreting the urachal mucinous neoplasm as a cystic metastasis from the colon cancer, perhaps due to a lack of awareness of urachal mucinous neoplasms. The potential risks of such an interpretation could include unnecessary systemic therapy, or a potential second surgical procedure for peritoneal cytoreduction and intraperitoneal chemotherapy (Sugarbaker procedure). This patient has been treated with only one abdominal surgery. He developed lung metastases that were surgically resected. There has been no evidence of local recurrence or peritoneal spread on surveillance imaging. We hope that this case will prove informative to pathologists, surgeons, and oncologists managing a similar scenario in the future, and we hope that this story will support those teams’ decisions to manage a case like this as two independent, concurrent neoplasms.
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.