Ovarian mucinous borderline tumor (mucinous atypical proliferative tumor) is a low malignant potential ovarian neoplasm originating from mucin-producing epithelial cells. Typically presents as a large (10-30 cm), multilocular cystic mass. Unlike serous borderline tumors, it is usually unilateral and contains fewer papillary projections. Due to its strong association with appendiceal mucinous tumors (pseudomyxoma peritonei), the appendix must be evaluated during surgery. Prognosis is generally excellent; 10-year survival in stage IA is >95%.
Age Range
25-55
Peak Age
40
Gender
Female predominant
Prevalence
Uncommon
Mucinous borderline tumors develop from mucin-producing metaplasia of the ovarian surface epithelium or from remnants of Brenner tumors/teratomas. The intestinal type is most common and contains goblet cells. The multilocular cystic architecture of the tumor, with locules containing mucin of varying viscosity, determines imaging characteristics: 'stained-glass' appearance on US, loculations of different densities create variable T1/T2 signal intensity on MRI. When mucin content is protein-rich, it appears hyperintense on T1. Large size (mean 15-20 cm) is typical; slow growth occurs due to mucin accumulation. The strong association with appendiceal mucocele/mucinous neoplasms is critical — when bilateral or peritoneal mucin is present, appendiceal origin (pseudomyxoma peritonei) must be considered. Classified as borderline when no invasive foci are present; areas of microinvasion or intraepithelial carcinoma do not affect prognosis.
Coexistence of loculations with different echogenicities in a large multilocular cystic ovarian mass. Each loculation shows different echogenicity due to different mucin viscosity — resembling stained glass windows. This pattern is highly characteristic of mucinous tumors and distinguishes them from serous tumors.
Large, multilocular cystic mass on US. Loculations of varying echogenicity create the 'stained-glass' appearance. Some loculations are anechoic (serous mucin), while others appear hypoechoic or mildly echogenic (thick mucin). This heterogeneous cystic pattern is characteristic of mucinous tumors.
Report Sentence
A large multilocular cystic mass is identified in the ovarian location with loculations of varying echogenicity ('stained-glass' appearance); mucinous borderline tumor should be the primary consideration.
Doppler US may show vascular flow in septa, but no high vascularity in distinct solid nodules is seen. Ring-of-fire pattern is typically absent. Even with septal vascularity, the absence or paucity of papillary projections distinguishes it from serous borderline.
Report Sentence
Doppler examination shows vascular flows within interlocular septa without a significant solid component or ring-of-fire pattern.
T1-weighted imaging shows loculations with variable signal intensity. Loculations containing watery mucin appear hypointense on T1, while those with high protein/mucin concentration appear hyperintense on T1. This variable T1 signal pattern is characteristic of mucinous tumors and distinguishes them from the homogeneous T1 hypointensity of serous tumors.
Report Sentence
Variable signal intensity is observed within the loculations on T1-weighted sequences (hypo- to hyperintense), indicating mucin concentration differences consistent with a mucinous neoplasm.
T2-weighted imaging shows a multilocular cystic mass. Most loculations are hyperintense on T2, but loculations containing thick mucin may show relatively lower signal (T2 shading). This T2 signal variability is typical for mucinous tumors. Septa appear as thin low-signal structures.
Report Sentence
A multilocular cystic mass is identified on T2-weighted sequences with T2 shading present in some loculations, indicating variable mucin viscosity.
Contrast-enhanced CT shows a large multilocular cystic mass. Loculations are seen at different densities (ranging 0-30 HU). Septa are thin and show smooth enhancement. Absence of significant solid component or papillary projections favors borderline. The large size of the mass and tendency for unilaterality are typical for mucinous type.
Report Sentence
Contrast-enhanced CT demonstrates a large multilocular cystic mass in the ovarian location with loculations of varying density and mild enhancement of thin smooth septa, consistent with a mucinous borderline tumor.
No significant diffusion restriction is seen on DWI. Mild signal increase may occur on DWI in loculations with mucinous content due to T2 effect (T2 shine-through), but no true restriction on ADC map. Presence of significant diffusion restriction should raise concern for invasive malignant transformation.
Report Sentence
No significant diffusion restriction is identified within the loculations of the mass on DWI, favoring a borderline neoplasm.
Contrast-enhanced MRI shows smooth, mild enhancement of thin septa. Thick (>3 mm), irregular septa or intense enhancement of distinct solid nodules are not seen — their presence would raise suspicion for invasive malignancy. In mucinous borderline, septal enhancement is typically homogeneous and regular.
Report Sentence
Contrast-enhanced MRI demonstrates thin, smooth enhancement of intra-mass septa without significant solid nodules or thick irregular septa.
Criteria
Epithelium showing goblet cells and intestinal differentiation. The most common subtype (85-90%). Has a strong association with appendiceal mucocele.
Distinct Features
Larger size (mean 18 cm), more loculations, fewer papillary projections. Appendiceal pathology may accompany; when bilateral or peritoneal mucin is present, appendiceal origin should be the primary consideration.
Criteria
Epithelium showing endocervical type mucin-producing cells and mixed (serous + mucinous) differentiation. Separated as a distinct category in WHO 2020 classification (seromucinous borderline).
Distinct Features
Smaller size, fewer loculations, may be associated with endometriosis. Bilaterality rate is higher than intestinal type. Imaging features may overlap with serous borderline.
Criteria
Stromal invasion limited to <5 mm or <10 mm2 area. Single or few foci of microinvasion. Prognosis is similar to pure borderline; recurrence rate in stage IA is <5%.
Distinct Features
Cannot be distinguished from pure borderline by imaging. Diagnosis is made by pathological examination. Clinical management is the same as pure borderline.
Criteria
High-grade atypia present within epithelium but no stromal invasion. Cribriform/micropapillary pattern observed. Prognosis similar to borderline but requires closer follow-up.
Distinct Features
Slightly thicker septa or more prominent papillary projections may be seen as imaging findings, but reliable differentiation is not possible. More frequent follow-up (every 6 months) is recommended.
Distinguishing Feature
Mucinous carcinoma shows thick irregular septa (>3 mm), significant solid component, and intense enhancement. Diffusion restriction is present in solid component on DWI. In borderline, septa are thin and regular.
Distinguishing Feature
Serous borderline is smaller, contains more prominent papillary projections, and has a higher tendency for bilaterality (30-40%). Mucinous borderline is larger, has more loculations and 'stained-glass' appearance, and is usually unilateral.
Distinguishing Feature
Endometrioma shows homogeneous T1 hyperintensity and T2 shading — typically single/few interconnected cysts. Mucinous borderline has variable T1 signal (between loculations), many multilocular compartments, and clinical endometriosis findings do not accompany.
Distinguishing Feature
Serous carcinoma is expected to show significant solid component, peritoneal carcinomatosis (omental cake), ascites, and bilateral involvement. Mucinous borderline is usually unilateral, ascites is minimal, and peritoneal implants are rare.
Urgency
routineManagement
surgicalBiopsy
Not NeededFollow-up
6-monthTreatment is complete surgical excision of the tumor. In young patients desiring fertility preservation, unilateral salpingo-oophorectomy or cystectomy may be sufficient. During surgery, the appendix must be examined and appendectomy performed when necessary (pseudomyxoma peritonei association). Peritoneal surfaces should be evaluated for mucin. No adjuvant therapy is needed in stage IA; follow-up at 6-month intervals is recommended in advanced stages. CA-125 may be mildly elevated or normal; CA 19-9 is a more sensitive marker.
Mucinous borderline tumors generally have excellent prognosis. Surgical excision is curative. Bilateral mucinous tumors should raise consideration for appendiceal primary. Invasive implants are a poor prognostic factor.