脐尿管低度恶性潜能黏液性囊性肿瘤：PathologyOutlines 专题全文Urachal mucinous cystic tumor of low malignant potential (PathologyOutlines topic; Textbook Updates 26 October 2026)

Scope: the full PathologyOutlines topic “Urachal mucinous cystic tumor of low malignant potential” with all 10 images and captions. The same 26 October 2026 Textbook Updates also covered factor VIII deficiency (hemophilia A), appendiceal neoplasms metastatic to ovary, polymorphous adenocarcinoma of salivary gland and testicular epidermoid cyst, which are not included.

Definition / general

• Glandular epithelial neoplasm arising from the urachus or urachal remnants, characterized by cystic architecture and mucinous epithelial lining with low grade cytologic atypia (Am J Surg Pathol 2014;38:1033)
• Morphologically resembles appendiceal low grade mucinous neoplasms and ovarian mucinous borderline tumors (Case Rep Gastrointest Med 2019;2019:1434838)

Essential features

• Urachal glandular neoplasm with low grade intestinal type mucinous epithelium and lack of infiltrative invasion
• May display papillary / villous epithelial proliferation
• Extravasated acellular stromal mucin is very common and should not be misinterpreted as invasion
  • Rupture may result in pseudomyxoma peritonei (Curr Oncol 2014;21:e155, Exp Ther Med 2023;26:555)
• Architectural complexity and presence or absence of invasion appears to be more biologically significant than cytologic atypia alone (Adv Anat Pathol 2016;23:71)
• Extensive sampling is critical to exclude small foci of carcinoma or focal microinvasion (Am J Surg Pathol 2014;38:1033)

Terminology

• Mucinous cystic tumor of low malignant potential (MCTLMP) (preferred)
• Designation of low malignant potential is preferred because these tumors demonstrate epithelial atypia exceeding that seen in benign cystadenomas but lack destructive stromal invasion required for a diagnosis of adenocarcinoma (Am J Surg Pathol 2014;38:1033)
• Borderline mucinous cystic tumor of urachus
• Low grade mucinous cystic tumor of urachus
• Urachal mucinous borderline tumor
• Historically grouped with urachal mucinous cystadenoma or mucinous adenocarcinoma before modern subclassification (Adv Anat Pathol 2016;23:71, Arch Pathol Lab Med 2019;143:258)

ICD coding

• Overlaps with urachal mucinous glandular neoplasms; coding may depend on institutional classification
• ICD-O: 8472/1 - mucinous cystic tumor of borderline malignancy
• ICD-10: Q64.4 - congenital anomaly of urachus; may be associated clinically
• ICD-11: 2F77 & XH2FF0 - neoplasm of uncertain behavior of male genital organs & mucinous cystic tumor of borderline malignancy
  • No universally standardized dedicated code identified at this time for MCTLMP specifically

Epidemiology

• Adults with a wide age range: 26 - 80 years old (Am J Surg Pathol 2014;38:1033, Int Cancer Conf J 2022;11:104)
• Urachal tumors overall account for < 1% of bladder malignancies (J Urol 2012;188:1102)
• Tumor size varies widely, with reported sizes ranging from ~2 to 8 cm (Am J Surg Pathol 2014;38:1033, Int Cancer Conf J 2022;11:104)
• No clear association between gender and risk of MCTLMP has been identified (Int Cancer Conf J 2022;11:104)

Sites

• Urachus / urachal remnants
• Most commonly involves the bladder dome or supravesical midline region between the bladder and umbilicus
• May extend toward the umbilicus or anterior abdominal wall (Adv Anat Pathol 2016;23:71)

Pathophysiology

• Persistence of the urachus leaves epithelial lined remnants susceptible to neoplastic transformation
• Thought to arise from glandular / intestinal metaplasia within urachal remnants (Adv Anat Pathol 2016;23:71, Am J Clin Pathol 2022;158:263)
• Demonstrates morphologic progression analogous to ovarian mucinous epithelial neoplasms
  • Mucinous cystadenoma → MCTLMP → MCTLMP with intraepithelial carcinoma → mucinous cystadenocarcinoma (with micro or frank invasion) (Adv Anat Pathol 2016;23:71, Am J Surg Pathol 2014;38:1033)

Etiology

• Associated with persistent urachus (embryologic remnant of the allantois)
• May arise secondary to chronic urine irritation of urachal remnant epithelium (Radiographics 2025;45:e240122, Adv Anat Pathol 2016;23:71)
  • Chronic urinary stasis, inflammation and infection within persistent urachal remnants have been proposed as contributors to neoplastic transformation

Diagrams / tables

Images hosted on other servers:

Bladder and umbilical connection

Clinical features

• Most often discovered as an incidental finding on imaging
• May present with hematuria, mucosuria, abdominal pain and palpable mass (Am J Surg Pathol 2014;38:1033, Cureus 2025;17:e90905, Arch Pathol Lab Med 2019;143:258)
• Rare cases present with pseudomyxoma peritonei after rupture or mucin spillage (Int Cancer Conf J 2022;11:104, Exp Ther Med 2023;26:555, Curr Oncol 2014;21:e155)
• Current classification schemes divide urachal mucinous cystic neoplasms analogously to ovarian mucinous epithelial tumors into the following (Adv Anat Pathol 2016;23:71, Am J Surg Pathol 2014;38:1033)
  • Mucinous cystadenoma
  • Mucinous cystic tumor of low malignant potential (MCTLMP)
  • MCTLMP with intraepithelial carcinoma
  • Mucinous cystadenocarcinoma with microinvasion
  • Mucinous cystadenocarcinoma with frank invasion

Diagnosis

• Diagnosis can be made on biopsy
• CT of abdomen / pelvis shows a cystic lesion extending from the umbilicus to the dome of the bladder (Int Cancer Conf J 2022;11:104, Medicine (Baltimore) 2017;96:e8740)
• Thorough histologic examination and extensive sampling are necessary to exclude infiltrative invasion or microinvasion (Am J Surg Pathol 2014;38:1033, Arch Pathol Lab Med 2019;143:258)
• Distinction from benign urachal cyst and invasive adenocarcinoma is critical

Laboratory

• Serum CEA and CA 19-9 levels have been elevated in some cases (Exp Ther Med 2023;26:555)

Radiology description

• Enhanced CT commonly demonstrates a unilocular or multiloculated supravesical cystic lesion without enhancement (Urol Case Rep 2025;61:103104, Exp Ther Med 2023;26:555)
• CT may demonstrate a stable cystic lesion adjacent to the bladder dome that can mimic a benign urachal cyst or diverticulum (Int Cancer Conf J 2022;11:104, Case Rep Gastrointest Med 2019;2019:1434838)
• Rim may be calcified (Case Rep Gastrointest Med 2019;2019:1434838)

Radiology images

Images hosted on other servers:

Multilocular cystic mass

Nonenhancing mass on CT

CT of calcified wall

Prognostic factors

• Architectural complexity and presence or absence of stromal invasion are key factors in classification and risk stratification of urachal mucinous neoplasms
• Presence or absence of stromal invasion is one of the most important determinants of biologic behavior
• Reported MCTLMP cases are typically free of recurrence or metastasis on follow up after complete surgical resection
• In contrast to MCTLMP, invasive urachal adenocarcinoma demonstrates substantially worse prognosis with reported 5 year survival rates near 45%
• References: Am J Surg Pathol 2014;38:1033, Adv Anat Pathol 2016;23:71, Int Cancer Conf J 2022;11:104

Case reports

• 38 year old man with incidental finding on ultrasound (Cureus 2025;17:e90905)
• 47 year old man with asymptomatic incidental mass (Cureus 2023;15:e37036)
• 54 year old man with dysuria and suprapubic discomfort (Cureus 2025;17:e78562)
• 74 year old man with lower abdominal pain with peritoneal pseudomyxoma (Exp Ther Med 2023;26:555)
• 77 year old man hospitalized for pneumonia (Urol Case Rep 2025;61:103104)

Treatment

• Complete surgical excision is the primary treatment and prognosis is generally favorable for localized noninvasive lesions (Am J Surg Pathol 2014;38:1033, Adv Anat Pathol 2016;23:71)
• Surgical management most commonly consists of partial cystectomy with en bloc excision of the urachal remnant and associated cystic lesion (Cureus 2023;15:e37036, Cureus 2025;17:e78562)

Gross description

• Urachal mucinous cystic tumors are typically well circumscribed unilocular or multilocular cystic lesions arising from the bladder dome or urachal remnant (Arch Pathol Lab Med 2019;143:258, Adv Anat Pathol 2016;23:71)
• Usually filled with abundant viscous mucinous or gelatinous material (Cureus 2025;17:e78562)

Gross images

Images hosted on other servers:

Bisected multiloculated cyst

Microscopic (histologic) description

• Epithelial stratification up to ~3 cell layers
• Lined by mucinous cuboidal to columnar epithelium
• Mild to moderate nuclear atypia and regions of nuclear pseudostratification
• Rare mitotic figures and low proliferative activity
• Mild to moderate cytologic atypia
• Pseudopapillary or villous architectural complexity
• Absence of stromal invasion
• Multiloculated or unilocular cystic lesion filled with mucinous material
• Thick fibromuscular cyst wall resembling urachal remnant
• May show goblet cells
• May demonstrate papillary, villous, tufted or pseudopapillary epithelial architecture
• References: Cureus 2025;17:e78562, Int Cancer Conf J 2022;11:104, Adv Anat Pathol 2016;23:71, Am J Surg Pathol 2014;38:1033, Am J Surg Pathol 2011;35:787, Arch Pathol Lab Med 2019;143:258

Microscopic (histologic) images

Contributed by Reima El Naili, M.D.

Positive stains

• CK20: diffuse, supporting intestinal type differentiation
• CDX2: diffuse, frequent
• SATB2: often
• CEA: variable (Urol Case Rep 2025;61:103104)
• β catenin: membranous or cytoplasmic staining pattern
• MUC5AC and MUC2 may be present in some areas (Cureus 2025;17:e78562)
• CK7 may be seen in ~30% of cases
  • β catenin and CK7 may be of help in distinguishing urachal from colorectal adenocarcinoma (Am J Surg Pathol 2011;35:787)
• References: Arch Pathol Lab Med 2019;143:258, Case Rep Gastrointest Med 2019;2019:1434838

Negative stains

• Nuclear β catenin
• GATA3
• ER / PR
• PSA
• AMACR
• p63 (Cureus 2023;15:e37036)
• References: Exp Ther Med 2023;26:555, Arch Pathol Lab Med 2019;143:258, Am J Surg Pathol 2011;35:787

Molecular / cytogenetics description

• TP53 and KRAS mutations occur in urachal carcinoma; however, molecular data for MCTLMP remain limited because of the rarity of these tumors (Oncotarget 2016;7:39293, Am J Clin Pathol 2022;158:263)

Sample pathology report

• Bladder, urachal diverticulum, excision:
  • Urachal mucinous cystic tumor of low malignant potential (MCTLMP) (see comment)
  • Comment: Histologic examination shows cystic spaces lined by stratified mucinous glandular epithelium with pseudopapillary architecture and low to moderate cytologic atypia, consistent with intestinal differentiation. No stromal invasion is identified. Provided immunohistochemical stains show the lesional cells to be positive for CK7, CK20, SATB2 and CDX2 but negative for GATA3. β catenin shows membranous staining pattern.

Differential diagnosis

• Diagnosis requires complete histologic evaluation of the cyst wall
• Correlation with imaging and clinical findings is necessary to exclude secondary involvement by colorectal or appendiceal mucinous neoplasms (Adv Anat Pathol 2016;23:71)
• MCTLMP with intraepithelial carcinoma:
  • Epithelium may have significant stratification and malignant cytologic features
    • Degree of cytologic atypia present is similar to villous adenomas
  • Stroma poor papillae
  • Architecturally more complex than conventional MCTLMP (e.g., papillary or cribriform growth)
  • Thorough sampling is required to rule out foci of invasive carcinoma
• Mucinous cystadenocarcinoma of the urachus:
  • Infiltrative stromal invasion
    • Microinvasion: invasive focus < 2 mm and comprising < 5% of tumor
    • Frank invasion: more extensive destructive stromal invasion
  • Destructive growth pattern
  • Marked cytologic atypia
• Mucinous cystadenoma of the urachus:
  • Single mucinous columnar epithelium lined cystic architecture
  • No atypia
• Villous adenoma of the urachus:
  • Exophytic villiform architecture
• Metastatic colorectal adenocarcinoma:
  • Often shows diffuse nuclear β catenin positivity
• References: Arch Pathol Lab Med 2019;143:258, Adv Anat Pathol 2016;23:71

Practice question #1

A cystic lesion arising from the dome of the bladder was resected from a 43 year old woman. Histologic examination shows multiloculated cystic spaces lined by mucinous columnar epithelium with mild to moderate atypia. What is the diagnosis?

1. Invasive mucinous cystadenocarcinoma of the urachus
2. Mucinous cystadenoma of the urachus
3. Mucinous cystic tumor of low malignant potential (MCTLMP) of the urachus
4. Villous adenoma

Practice answer #1

C. Mucinous cystic tumor of low malignant potential (MCTLMP) of the urachus. MCTLMP demonstrates cystic mucinous epithelium with mild to moderate cytologic atypia and limited architectural complexity such as pseudopapillary growth or stratification. Answer D is incorrect because villous adenoma typically shows exophytic villous architecture with fibrovascular cores rather than multiloculated cystic spaces. Answer B is incorrect because mucinous cystadenoma lacks significant atypia and epithelial stratification. Answer A is incorrect because invasive mucinous cystadenocarcinoma requires stromal invasion.

Reference: Urachal mucinous cystic tumor of low malignant potential