Ovarian mucinous cystadenoma is a common benign epithelial ovarian tumour, often demonstrating large multiloculated cystic appearance on imaging, with thick septations and nodularity being indicative of potential malignancy.
Description
Ovarian mucinous cystadenoma is a benign neoplasm of the ovary, characterised by the production of mucin by columnar epithelial cells lining the cystic tumour. It is the second most common type of benign epithelial ovarian tumour.
Pathogenesis
The precise pathogenesis of ovarian mucinous cystadenoma is unclear, but it is thought to arise from the ovarian surface epithelium or from the invagination of this epithelium to form cortical inclusion cysts.
Subtypes
No specific subtypes of ovarian mucinous cystadenoma have been delineated.
Epidemiology, Risk Factors & Associations
- Ovarian mucinous cystadenomas typically occur in the third to fifth (perimenopausal) decades of life
- No significant risk factors or associations have been definitively identified.
Clinical Features
- Most patients are asymptomatic, but larger tumours may cause abdominal distention or discomfort.
- Unlike their malignant counterparts, benign mucinous cystadenomas are typically unilateral.
- Massive tumours can present with weight gain and distended abdomen
Complications
- Mucinous tumours are usually benign compared to serous tumors. Risk of malignant transformation to mucinous cystadenocarcinoma is therefore low, but does exist.
- Larger tumours may result in torsion, causing acute abdominal pain.
- Pseudomyxoma peritonei
Pathological Features
Histopathology
- Macroscopic: Large, multiloculated cystic masses filled with mucin.
- Microscopic: Lined by tall columnar epithelium with apical mucin.
Biochemistry
- CA 125 not useful for mucinous tumours (30% false-negative)
Radiological Features
General Features
- Characteristically demonstrates a large, usually multilocular cystic mass.
- May be bilateral
- Can fill entire pelvis and extend into upper abdomen
- The presence of thick septations, nodularity, or solid components may suggest malignant transformation.
US
- B-mode: Large, unilocular or multilocular cystic mass with low-level echoes
- Colour: Thick vascular septations
CT
- Non-contrast: Low attenuation cystic mass.
- Contrast-enhanced: Peripheral enhancement of cystic walls/septations.
MRI
- T1WI: Low signal intensity.
- T2WI: High signal intensity.
- T1 C+: Peripheral enhancement of cystic walls/septations.
Grading and Staging
As a benign tumour, grading and staging are not typically relevant to mucinous cystadenomas.
Diagnosis
Diagnosis is generally made based on a combination of clinical, radiological, and histopathological findings.
Differential Diagnosis
- Mucinous cystadenocarcinoma: Presence of solid components or thick septations and nodularity may suggest malignancy.
- Serous cystadenoma: Typically demonstrate smaller, numerous loculations. Can be bilateral, but less likely than mucinous cystadenoma. Typically smaller than mucinous cysadenoma. More malignant and more likely to be associated with peritoneal carcinomatosis. Demonstrates high T1 and lower T2 on MRI compared to mucinous.
- Endometriomas: Tend to be smaller, unilateral, and with ‘ground glass’ echogenicity on ultrasound.
- Gastrointestinal metastasis: Bilateral ovarian mucinous masses
Management
Surgical resection is the treatment of choice. Large cysts may require an oophorectomy. If malignancy is suspected, staging and debulking surgery may be necessary.