Ovarian serous neoplasms are the commonest of four general types of the epithelial ovarian tumours, and are more prevalent than the mucinous ovarian tumours.
Serous ovarian neoplasms are subdivided into benign, borderline, and malignant lesions according to their malignant potential and clinical behaviour (see Pathology - Classification section below).
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Epidemiology
Approximately 60% are benign and ~15% of borderline malignancy; These occur most commonly in women of reproductive age. The malignant tumours comprise 25% of cases and tend to occur in older patients.
Pathology
Serous ovarian tumours are defined by a histologic resemblance to normal Fallopian tubal epithelium 5.
Classification
The 2014 WHO classification system for serous ovarian neoplasia identifies three categories of tumour:
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benign - no cellular proliferation or invasion
serous surface papilloma
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borderline - cellular proliferation + minor nuclear atypia without invasion
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malignant - cellular proliferation + nuclear atypia + stromal invasion
high grade serous carcinoma - most common serous carcinoma (85-90% serous carcinomas), highest associated mortality 6
Radiographic features
Imaging evaluation may be performed preferably with ultrasound or MRI, with CT usually reserved for staging purposes. In general, the cell type (e.g. serous, mucinous) often cannot be determined on the imaging basis of appearances.
Serous ovarian tumours are typically smaller than mucinous tumours on presentation. They are typically unilocular and homogeneous. They are often bilateral, and this is particularly so for the malignant subtypes. Psammomatous calcification is a feature of serous, but not mucinous subtypes.
Features that suggest a malignant over a benign cystic neoplasm include:
large cystic mass
thick irregular walls and septa
papillary projections
large soft tissue component
evidence of invasive spread or adenopathy
Differential diagnosis
Considerations include:
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usually smaller
thin walls with no septations
tend to change or resolve in the next menstrual cycle
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ovaries can be individualised apart from the cyst
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tend to be multiseptated
often larger than serous tumours
monolateral rather than bilateral
cystic loculi with variable signal intensities on MRI giving the appearances of "stained glass"