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Serous cystadenoma is a benign epithelial ovarian neoplasm characterized by cysts lined with serous (non-mucinous) epithelium resembling fallopian tube lining.

It accounts for about 20–25% of all benign ovarian epithelial tumors.

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Etiopathology

• Cell of origin: Ovarian surface epithelium (coelomic epithelium) undergoing Müllerian differentiation.
• Epidemiology:
  • Most common in women aged 20–50 years (reproductive and perimenopausal age group).
  • Bilaterality in ~20% of cases (more common than mucinous cystadenoma).
• Molecular aspects: Generally lacks the KRAS or BRAF mutations seen in borderline/malignant serous tumors.
• Behavior: Benign, but related to the spectrum of serous tumors (borderline serous tumor → serous carcinoma).

Clinical Features

• Often asymptomatic, discovered incidentally on pelvic exam or imaging.
• Large lesions may cause abdominal distention, pelvic pain, pressure symptoms (urinary frequency, constipation).
• Rarely torsion, rupture, or hemorrhage.

Pathology

Gross Pathology

• Usually unilateral (though 20% bilateral).
• Smooth-surfaced cystic mass, thin-walled, containing clear watery fluid.
• Size: variable, usually 5–15 cm, smaller than mucinous cystadenomas.
• May be unilocular or multilocular.