Senior oncologist explains what is Struma Ovarii and how this rare ovarian tumour is associated with hyperthyroidism

Struma ovarii is a rare ovarian tumour made of thyroid tissue. While often benign, it can sometimes cause hyperthyroidism or mimic ovarian cancer. (Image: Pexela)

Struma ovarii is a rare ovarian neoplasm consisting of thyroid tissue. It constitutes only 0.5 percent of all ovarian tumours and mainly occurs in women aged between 40 and 60 years. In many cases, the tumour is benign (non-cancerous) and only in one ovary; about 5 percent may be cancer and spread.

Most women with struma ovarii are asymptomatic, or do not have any visible symptoms. But if a tumour gets bigger, it can also press against other organs nearby and cause abdominal pain or bloating, as well as problems with bowel and urinary function.

Hormonally active thyroid tissue can be found inside the tumour in 5–20 percent of cases, which is what results in hyperthyroidism (12). Symptoms of an overactive thyroid can include rapid heart rate, tremors, anxiety, hypertension, weight loss and sleeplessness. In rare cases, fluid can build up in the abdomen and around the lungs as a result of struma ovarii, even if the tumour is not cancerous (a syndrome called “pseudo-Meigs”).

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Dr Sudha Sinha, Clinical Director & HOD, Senior Consultant, Medical Oncology & Hemato-Oncology at Yashoda Hospitals Hyderabad discusses diagnosis and preventative measures with Moneycontrol.

Diagnosis

Routine gynaecological examinations lead to an early identification of a struma ovarii in many cases. Pelvic ultrasound is generally the first test, although other imaging (CT or MRI) might be done to know how far the tumour has spread. Struma ovarii may be wrongly diagnosed in some cases, considering its imaging can appear similar to ovarian cancer.

If a woman shows signs of hyperthyroidism, doctors typically begin by testing for the thyroid gland. If the thyroid is normal, an iodine scan that determines whether the ovary (as opposed to the thyroid gland) is responsible for excessive hormone production may be performed.

Treatment Options

The primary treatment of struma ovarii is surgical intervention. The choice depends on a woman’s age, fertility issues and whether cancer is suspected.

Fertility preservation: In younger women, it may be possible to preserve the ovary but remove only the ovarian cyst.

Extensive tumours: If a tumour is larger or considered suspicious of causing problems, the affected ovary may be removed.

Postmenopausal women: Often, removal of the uterus and both ovaries is advised.

The preferred technique is laparoscopic, when feasible. In case there is hyperthyroidism, most often the thyroid hormone levels are normalized using medication prior to surgery. If the ratio of true ovarian tissue to tumour is high and only a mild increase in markers is seen, further treatment may not be necessary.

When the struma ovarii part becomes malignant, additional procedures such as thyroid resection with lymphadenectomy, radioiodine therapy or even revision surgery might be needed.

Risk of Recurrence

Struma ovarii is usually cured by surgery, but it may recur. Risk factors for recurrence have been described, including larger tumour size (>4 cm), extraovarian spread, aggressive histologic appearance and specific genetic mutations. Close long-term follow-up is critical to detect recurrences, particularly in those women who have more advanced or aggressive disease at the outset.

Struma Ovarii and Hyperthyroidism

Most struma ovarii tumours are not hormonally active; however, some may overproduce thyroid hormone and cause hyperthyroidism. This can present with complaints of palpitations, anxiety, weight loss and insomnia. In these cases medication is required to stabilise the thyroid function prior to surgical excision of the tumour (usually via a laparoscopic approach).

FAQs about Struma Ovarii:

1. What is struma ovarii?
Struma ovarii is a rare ovarian tumour composed of thyroid tissue.

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2. Who is at risk of developing struma ovarii?
It mainly occurs in women aged between 40 and 60 years.

3. Is struma ovarii usually benign or cancerous?
In most cases, struma ovarii is benign, but about 5 percent can become cancerous.

4. What are the symptoms of struma ovarii?
Most women are asymptomatic, but larger tumours can cause abdominal pain, bloating, and issues with bowel and urinary function.

5. How is struma ovarii diagnosed?
Routine gynaecological exams, pelvic ultrasound, and other imaging tests like CT or MRI help in diagnosing struma ovarii.

6. What treatment options are available for struma ovarii?
Surgical intervention is the primary treatment, with options varying based on the patient's age, fertility concerns, and whether cancer is suspected.

7. Can struma ovarii cause hyperthyroidism?
Yes, in 5–20 percent of cases, the tumour may contain hormonally active thyroid tissue, leading to hyperthyroidism.

8. What is the risk of recurrence for struma ovarii?
While usually cured by surgery, struma ovarii can recur, especially in cases with larger tumours, extraovarian spread, or aggressive histologic appearance.

Disclaimer: This article, including health and fitness advice, only provides generic information. Don’t treat it as a substitute for qualified medical opinion. Always consult a specialist for specific health diagnosis.