Practice Essentials
Struma ovarii is a rare ovarian tumor that was first described in 1899. It is defined by the presence of thyroid tissue comprising more than 50% of the overall mass. It most commonly occurs as part of a teratoma, but may occasionally be encountered with serous or mucinous cystadenomas. [1] Strumae ovarii comprise 1% of all ovarian tumors and 2-5% of ovarian teratomas.
Several variants of the tumor exist. Benign strumosis is a rare version where mature thyroid tissue implants are present throughout the peritoneal cavity. Strumal carcinoid is defined by the presence of carcinoid tissue within a struma ovarii. The vast majority of strumae ovarii are benign, but malignant disease is found in a small percentage of cases, the most common being papillary thyroid carcinoma.
Signs and symptoms
The symptoms of struma ovarii are similar to those of other ovarian tumors and are nonspecific in nature. They can include the following:
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Abdominal pain
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Palpable abdominal mass
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Abnormal vaginal bleeding
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Pseudo-Meigs syndrome (ascites in the setting of hydrothorax)
See Presentation for more detail.
Diagnosis
The tumor can be characterized by imaging, but the final diagnosis is made by pathological and histological examination. Pathological examination reveals thyroid tissue as the major component of the mass and is most commonly found in a teratoma.
See Workup for more detail.
Management
Surgical resection remains the definitive treatment for benign disease, and surgery with adjuvant radioiodine therapy has been shown to be successful in treating metastatic and recurrent disease. [3]
See Treatment for more detail.
Patient education
For excellent patient education resources, visit eMedicineHealth's Thyroid and Metabolism Center. Also, see eMedicineHealth's patient education article Thyroid Problems.
Epidemiology
United States statistics
Struma ovarii is rare. Approximately 1% of all ovarian tumors and 2.7% of all dermoid tumors are classified as struma ovarii. [4]
Race-, sex-, and age-related demographics
Because of its rarity, no clear racial predilection for struma ovarii has been determined.
Defined as a tumor of ovarian origin, struma ovarii occurs exclusively in genetic females.
Struma ovarii typically presents between the ages of 40-60 and rarely occurs before puberty.
Prognosis
For the vast majority of patients, the struma is benign, and the prognosis is excellent. Even in malignant cases, adjuvant iodine-131 ablation with surgical extirpation has proven curative. Recurrences may be detected using iodine-123 scanning, and repeat iodine radioablation can lead to extended disease-free survival.
In an analysis of 88 patients with malignant struma ovarii, several factors were identified as being associated with recurrence or extraovarian spread. These include adhesions, peritoneal fluid of 1 liter or more, ovarian serosal rent, a papillary histology, or a struma component 12 cm or more. The overall survival rate for all patients is 89% at 10 years and 84% at 25 years. [5]
In a retrospective study of 194 malignant struma ovarii cases, the 5-, 10-, and 15-year overall survival rates were 91.4%, 87.7%, and 83.5%, respectively. The researchers identified International Federation of Gynecology and Obstetrics (FIGO) stage IV, age 45 years or older, and poor differentiation of tumors as predictors of a worse prognosis. [6]
Morbidity/mortality
Malignancy is defined by various criteria in different studies, principally differing on classifying struma as either a thyroid or ovarian cancer. In the most recent World Health Organization classification, malignant struma ovarii are included in the thyroid tumor group. [4] Several other types of tumors, such as Brenner tumor or cystadenoma, may also be found with a struma. Note the following:
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Malignant change seems to occur in about a third of cases [7]
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Metastatic spread, which follows the pattern of ovarian cancer, occurs in approximately 5% of malignant cases [7]
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Survival rates are excellent [8]
Although the tumor is predominately composed of thyroid tissue, thyrotoxicosis is seen in only 5% of all cases. Only 1 case of thyrotoxicosis resulting from peritoneal strumosis has been reported. [9]
In a study of 68 patients with malignant struma ovarii, Goffredo et al found excellent disease-specific survival rates for the condition no matter which treatment—unilateral oophorectomy, bilateral oophorectomy, oophorectomy and omentectomy, or debulking surgery—was used. The report, which utilized the Surveillance, Epidemiology, and End Results (SEER) database of the National Cancer Institute, also determined that the risk of aggressive thyroid cancer in patients with malignant struma ovarii is high. The overall 5-, 10-, and 20-year survival rates in the study were 96.7%, 94.3%, and 84.9%, respectively, with only one of the deaths that occurred being attributed to malignant struma ovarii. The investigators found, however, that six patients (8.8%) were diagnosed concomitantly or subsequently with thyroid cancer, with two thirds of the thyroid cancers growing beyond the thyroid gland. All of the thyroid cancer patients were still alive at the last follow-up. [8]
Complications
Significant changes in thyroid function may occur in the immediate perioperative period.
