Serous cystadenoma is the most common benign epithelial tumor of the ovary. It typically presents as a thin-walled, unilocular or oligolocular cystic lesion. The cyst content is serous (clear, watery) fluid. On ultrasound, it may mimic a simple cyst but is generally larger (>5 cm). On MRI, it shows homogeneous fluid signal hypointense on T1 and hyperintense on T2. On CT, homogeneous near-water density content with a thin, smooth wall and minimal or no enhancement is seen. It can occur in both premenopausal and postmenopausal women. The risk of malignant transformation is low, but careful follow-up is needed for large lesions and in older patients. It can be bilateral (12-20%). Treatment is generally surgical excision; laparoscopic cystectomy or oophorectomy is preferred.
Age Range
20-60
Peak Age
40
Gender
Female predominant
Prevalence
Common
Serous cystadenoma originates from the ovarian surface epithelium (serosa) or fallopian tube-type müllerian epithelium. It is lined by a single-layer epithelium producing tubal-type serous secretion. This epithelium produces watery, protein-poor serous fluid — therefore cyst content appears anechoic on ultrasound, near-water density (~0-15 HU) on CT, and T1 hypointense + T2 hyperintense on MRI. The thin wall is well-defined because the epithelium shows benign proliferation without stromal invasion. Enhancement is minimal or absent because thin wall vascularity is limited — this feature is critical for differentiation from malignant lesions (which show avid enhancement with papillary projections, thick walls, and solid components). Serous cystadenomas can rarely reach giant sizes (>20 cm), increasing the risk of mass effect and torsion.
On ultrasound, a <3 mm thin, smooth-walled, single-locule, completely anechoic cystic lesion with posterior acoustic enhancement. Distinguished from simple cyst by size (serous cystadenoma generally >5 cm). Absence of solid component, papillary projection, and increased Doppler vascularity supports benign character.
Thin-walled (<3 mm), unilocular, anechoic cystic lesion. Posterior acoustic enhancement is present. No internal echoes, debris, or solid components. Similar to simple cyst but size is generally larger (>5 cm, often 5-15 cm).
Report Sentence
A ___ x ___ mm thin-walled (<3 mm), unilocular, anechoic cystic lesion is seen in the right/left ovary, consistent with serous cystadenoma.
Minimal or no vascularity in the cyst wall and septa on Doppler ultrasound. No ring-of-fire pattern. A thin peripheral vascular rim may rarely be seen, but irregular or intense vascularity favors malignancy.
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No significant vascularity is detected in the cyst wall and septa on Doppler examination; no ring-of-fire pattern.
Some serous cystadenomas may be oligolocular — containing thin (<3 mm), smooth septa. Septa appear as homogeneous, echogenic lines. No nodularity, irregularity, or thickening (>3 mm). Septum count is generally 1-3.
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___ thin (<3 mm), smooth septa are seen within the cystic lesion; no nodularity or irregularity.
Homogeneous cystic lesion with near-water density (0-15 HU) on CT. Wall is thin, smooth, with minimal or no enhancement. No solid component, papillary projection, or mural nodule. Calcification is rare. Minimal density difference between wall and cyst content on contrast-enhanced series.
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A ___ x ___ mm cystic lesion with near-water density (___ HU) and thin wall is seen in the right/left adnexal region; no solid component or mural nodule is detected.
Markedly hyperintense, homogeneous fluid signal on T2W. Fluid signal intensity is similar to free water. No nodularity in wall or septa. Signal homogeneity supports that cyst content is pure serous fluid — hemorrhagic or proteinaceous content shows heterogeneous or lower signal on T2.
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A thin-walled cystic lesion measuring ___ x ___ mm showing homogeneous hyperintense fluid signal on T2W is seen in the right/left ovary.
Homogeneous hypointense fluid signal on T1W. No hyperintensity — this excludes hemorrhagic content (subacute blood = T1 hyperintense) or proteinaceous/mucinous content (T1 mildly hyperintense). No signal change on fat-sat sequences — no fat content is present (dermoid/teratoma excluded).
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The cystic lesion shows homogeneous hypointense signal on T1W; no hemorrhagic or proteinaceous content is detected.
No diffusion restriction in cyst content on diffusion-weighted imaging. High signal on ADC map (free diffusion). Presence of diffusion restriction suggests abscess (purulent content, high viscosity) or solid tumoral component.
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No diffusion restriction is detected in the cyst content on DWI; high signal is seen on the ADC map.
Criteria
Single-compartment, no septa, simple cyst appearance. Most common type (60-70%).
Distinct Features
Distinguished from simple cyst by size — generally >5 cm. Persistent cystic lesion >5 cm in postmenopausal woman increases the probability of serous cystadenoma.
Criteria
Divided by 2-4 thin septa, containing few locules. Septa <3 mm, smooth, minimal enhancement.
Distinct Features
Differentiation from mucinous cystadenoma: serous type contains fewer, thinner septa. Mucinous type shows numerous locules, stained-glass appearance, and thicker septa.
Criteria
Contains serous epithelium + fibrous stromal component. A solid-appearing fibrous nodule may be present within the cystic lesion.
Distinct Features
On MRI, fibrous component appears markedly T2 hypointense (fibrous tissue has short T2). Minimal enhancement on CT. Solid component may raise malignancy suspicion — but T2 hypointensity and lack of enhancement of fibrous nodule support benign character.
Distinguishing Feature
Simple (functional) cyst is generally <5 cm and shows spontaneous resolution within 2-3 cycles. Serous cystadenoma is larger (>5 cm), persistent, and spontaneous regression is not expected. Both lesions are anechoic with thin walls.
Distinguishing Feature
Mucinous cystadenoma is multilocular with stained-glass appearance (locules of varying echogenicity), larger (>10 cm common) and thicker septa (>3 mm). Serous cystadenoma is unilocular/oligolocular, homogeneously anechoic, thin septa, and smaller.
Distinguishing Feature
Serous borderline tumor shows papillary projections (papillary protrusions on cyst wall or septa) — these are ABSENT in serous cystadenoma. Papillary projections enhance and show vascularity on Doppler. Presence of papillary projections suggests borderline or malignant diagnosis.
Distinguishing Feature
Serous carcinoma shows prominent solid component, thick irregular wall (>3 mm), intense enhancement, ascites, and peritoneal implants. Serous cystadenoma has no solid component, thin smooth wall, minimal enhancement; ascites and peritoneal implants are not expected.
Urgency
routineManagement
surgicalBiopsy
Not NeededFollow-up
6-monthSerous cystadenoma is a benign lesion. For small (<5 cm), asymptomatic lesions, 6-month US follow-up may be sufficient. For large (>5 cm), persistent, or symptomatic lesions, surgical excision (laparoscopic cystectomy or oophorectomy) is recommended. All persistent cystic lesions in postmenopausal patients require surgical evaluation. Malignant transformation risk is very low, but histopathological confirmation is recommended for serous cystadenofibroma due to the presence of solid component.
Serous cystadenoma is a benign ovarian tumor. Symptoms are usually size-related (abdominal distension, pressure). Surgical excision is curative. Differentiating benign serous cystadenoma from borderline/malignant serous tumors is important.