A 31-year-old woman with a 9 cm left ovarian mass develops palpitations, weight loss and tremor. Free T4 is elevated, TSH is suppressed, and thyroid antibodies are negative. Neck examination and ultrasound are normal. Which ovarian tumour explains these findings?

• A Sclerosing stromal tumour
• B Serous cystadenofibroma
• C Adult granulosa cell tumour
• D Struma ovarii ✓

Explanation

Struma ovarii is a monodermal mature teratoma composed predominantly of functional thyroid tissue. It can secrete thyroid hormone and cause biochemical and clinical thyrotoxicosis while the neck is normal, because the hormone source is the ovarian mass. Treatment is excision of the adnexal mass. Granulosa cell tumours produce oestrogen, sclerosing stromal tumours are typically non-functioning or mildly oestrogenic, and serous cystadenofibromas are inert epithelial lesions.

Reference: Williams Gynecology, 4th ed.

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Written and medically reviewed by the StethoPrep medical team.