Ovarian Fibroma and Meigs Syndrome
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Direct answer
Ovarian fibroma is a benign, solid sex cord-stromal tumour of the ovary, usually unilateral and typically found in middle-aged women. Meigs syndrome is the combination of this tumour with ascites and a pleural effusion, most often on the right side, and all three features resolve after the tumour is removed. Because the picture mimics ovarian cancer, a frozen section is usually sent before the extent of surgery is decided.
What you must remember
- Histology: A benign sex cord-stromal tumour made of spindle-shaped stromal cells; a fibrothecoma also contains theca-like cells.
- Ultrasound: A solid, hypoechoic, usually unilateral mass, often with posterior acoustic shadowing.
- Meigs triad: Benign ovarian fibroma or fibrothecoma, ascites and hydrothorax.
- Side of hydrothorax: Usually right-sided, although it can be left-sided or bilateral.
- Pseudo-Meigs: The same ascites and effusion caused by a pelvic tumour other than a fibroma or fibrothecoma, such as a malignant ovarian tumour, struma ovarii or a uterine fibroid; fluid resolves only if the tumour is benign and removed.
- CA-125: Often raised by ascites itself, so it can wrongly suggest malignancy.
- Management: Unilateral salpingo-oophorectomy or oophorectomy, with frozen section to exclude malignancy first.
Working through the features of a solid pelvic mass
A 55-year-old woman has a solid right adnexal mass, ascites and a right pleural effusion. The table compares the picture with malignant disease to show which features point where. Right-sided effusion is the detail most often asked in examinations.
| Feature | Meigs syndrome | Malignant ovarian tumour |
|---|---|---|
| Ovarian mass | Benign fibroma or fibrothecoma | Malignant epithelial or other tumour |
| Ascites | Present | Present, often with peritoneal spread |
| Pleural effusion | Usually right-sided | May be bilateral |
| After removal | Ascites and effusion resolve | Fluid persists or recurs |
| Frozen section | Benign | Malignant |
Resolution of ascites and effusion after removal of a solid ovarian tumour is the key discriminating feature. Persistent fluid after a benign-looking operation should prompt a search for another cause or occult malignancy.
Ascites is present in both groups, so it cannot by itself separate benign from malignant disease. Surgeons therefore look at the whole pattern rather than any single feature. A rise in CA-125 from ascites alone should not be read as evidence of cancer.
Where the exam tries to catch you
The classic trap is to read ascites and pleural effusion as metastatic disease.
- Trap: Assuming ascites with a pleural effusion always means ovarian cancer Correct: Meigs syndrome produces the same picture from a benign fibroma, and the diagnosis is confirmed when the fluid resolves after removal.
- Trap: Believing a raised CA-125 settles the diagnosis Correct: Ascites itself raises CA-125, so the marker cannot separate Meigs syndrome from cancer.
- Trap: Expecting the hydrothorax to be left-sided Correct: The effusion in Meigs syndrome is classically right-sided, though the textbooks accept other sides.
Frequently asked questions
What are the three components of the Meigs triad?
The Meigs triad consists of a benign ovarian tumour, most often a fibroma or fibrothecoma, ascites and a pleural effusion. The effusion is usually on the right side. All three features resolve after the ovarian tumour is removed.
Which side is hydrothorax usually found on in Meigs syndrome?
Hydrothorax in Meigs syndrome is usually right-sided, although it can occur on the left or be bilateral. The fluid is thought to pass from the ascites through the diaphragm. Right-sided hydrothorax is therefore the classic answer in exams.
How does pseudo-Meigs syndrome differ from Meigs syndrome?
Pseudo-Meigs syndrome has ascites and pleural effusion associated with a pelvic tumour other than a fibroma or fibrothecoma, such as a malignant ovarian tumour, struma ovarii or a uterine fibroid. Fluid resolves only if the tumour is benign and removed. Pseudo-Meigs syndrome therefore needs histology to define the underlying pathology.
Does ascites in Meigs syndrome resolve after surgery?
Yes, the ascites and pleural effusion usually resolve completely after removal of an ovarian fibroma. Persistent fluid after surgery should prompt a search for malignancy or another cause. Resolution is the feature that confirms the diagnosis of Meigs syndrome.
Why is frozen section needed before surgery for a suspected ovarian fibroma?
Frozen section confirms that a solid ovarian mass is benign before the surgeon decides the extent of the operation. Because ascites can mimic peritoneal cancer, a malignant result changes the procedure to a staging operation. This avoids an inadequate operation for an unrecognised cancer.