A 30-year-old woman comes to the office for evaluation of irregular menses. The patient has had increasingly irregular menses over the past 6 months, and hot flashes and unintentional weight loss for the past few months. She has also had intermittent lower abdominal pain that is usually worse after increased physical activity. The patient has no chronic medical conditions and takes no daily medications. On examination, the abdomen is nontender. A pelvic examination shows a left adnexal mass and a small uterus. TSH is low and a urine pregnancy test is negative. Pelvic ultrasound reveals a 6-cm left ovarian mass. The mass is surgically removed, and gross examination of the specimen shows a cystic lesion with an oily substance. Which of the following cell types is the most likely source of the neoplasm in this patient?
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Ovarian tumors are classified based on their predominant cell type, which determines their classic clinical symptoms and gross appearance. Ovarian tumor types include:
Surface epithelial-stroma: composed of cells that support the normal ovarian structure for ovulation (eg, serous, mucinous epithelial cells).
Sex cord-stroma: composed of cells that support and surround the oocyte. These cells secrete sex hormones including estrogen (granulosa cells) and testosterone (Sertoli-Leydig cells).
Germ cell: composed of cells that can develop into an embryo or placenta. These tumors are composed of varying amounts of germ layers (ie, endoderm, mesoderm, ectoderm), yolk sac, or placenta (eg, chorion). They often have associated hormonal activity (eg, increased hCG, alpha fetoprotein).
This patient's unintentional weight loss, hot flashes, irregular menses, and low TSH level are consistent with thyrotoxicosis (ie, abnormally high circulating thyroid hormone levels). In the setting of an adnexal mass, this presentation is classic for struma ovarii, an ovarian germ cell tumor composed of >50% mature thyroid tissue (derived from the endoderm) that can secrete thyroid hormone. On gross examination, struma ovarii typically appears as an oily (eg, sebaceous) cystic mass. Microscopic examination reveals thyroid follicles filled with colloid and surrounded by ovarian stroma.
(Choice A) Endometriomas occur when ectopic endometrial tissue and old blood collect in the ovary. Patients can have lower abdominal pain; however, they typically have regular menses. In addition, endometriosis is not associated with hot flashes, weight loss, or abnormal TSH levels.
(Choice C) Granulosa cell tumors are a type of sex cord–stroma tumor that secrete estrogen and inhibin, thereby suppressing FSH release and causing irregular menses. They do not secrete thyroid hormone and therefore do not cause thyrotoxicosis.
(Choice D) Ovarian fibromas are sex cord–stroma tumors that arise from ovarian fibroblasts, which have no endocrine activity and therefore do not affect TSH levels. Fibromas are typically solid, not cystic.
(Choice E) Ovarian thecomas are benign sex cord–stroma tumors composed of cells histologically similar to thecal cells. Therefore, thecomas typically increase circulating estrogen (causing abnormal uterine bleeding) but do not cause thyrotoxicosis.
Educational objective:
Struma ovarii is an ovarian germ cell tumor composed of >50% mature thyroid tissue that can secrete thyroid hormone. Therefore, struma ovarii can be a rare cause of thyrotoxicosis (eg, weight loss, irregular menses, low TSH level).