eMedicine Specialties > Obstetrics and Gynecology > General Gynecology

Struma Ovarii

Updated: Oct 26, 2009

Introduction

Background

Struma ovarii was first described in 1899 and is extremely rare, with only 150 reported cases in the medical literature. Because of the nature of thyroid tissue in the ovary, the definition of malignancy and the management of struma have been debated by those who believe the tumor favors an ovarian versus a thyroid neoplasm.

Struma ovarii is defined by the presence of an ovarian tumor containing thyroid tissue as the predominant cell type. They typically occur as part of a teratoma but may occasionally be encountered with serous or mucinous cystadenomas¹. Malignant transformation is rare, but it is usually defined on histologic criteria. Benign strumosis is a rare version of mature thyroid tissue implants throughout the peritoneal cavity. Strumal carcinoid is defined by the presence of carcinoid tissue within a struma and is exceptionally rare.

Pathophysiology

On gross examination, the struma is brown or green-brown and solid, but it can also be partly or entirely cystic, filled with gelatinous fluid. The contralateral ovary may contain another teratoma, but the struma is rarely bilateral. Most strumal tissue is not functionally active, and cases associated with thyrotoxicosis can be due to autoimmune stimulation of the normal thyroid gland.

Frequency

United States

Between 0.8-3% of teratomas contain functional thyroid tissue or thyroid tissue occupying most of the mass. They are thus classified as a struma ovarii. Approximately 15% of teratomas have a small, nonsignificant focus of thyroid tissue.

Mortality/Morbidity

Malignancy is defined by various criteria in different studies, principally differing on classifying struma as either a thyroid or ovarian cancer. Several other types of tumors, such as Brenner tumor or cystadenoma, may also be found with a struma.

Malignant change seems to occur in about a third of cases.
Metastatic spread, which follows the pattern of ovarian cancer, occurs in approximately 5% of malignant cases.

Race

Because of its rarity, no clear racial predilection for struma ovarii has been determined.

Age

The fifth and sixth decades are the ages of peak frequency.
Struma ovarii rarely occurs before puberty.

Clinical

History

Most strumas are found during pathologic examination of an excised pelvic mass. A patient with a struma typically presents with the symptoms of a pelvic mass, including pain, pressure, and irregular menses.

Only 8% of patients with strumas present with clinical hyperthyroidism. Associated and significant thyroid function abnormalities are present in 25-33% of patients.
Pleural effusion and ascites are sometimes present.

Physical

A struma always occurs as a pelvic mass, which may be palpable on physical examination, depending upon size and location. Approximately 15% of patients present with enlargement of the thyroid gland.

Differential Diagnoses

Hyperthyroidism

Workup

Laboratory Studies

CBC count
Blood type and screen
A cancer antigen 125 (CA125) test is usually ordered in patients with solid pelvic masses. Results should be within normal limits.
Thyroid function tests are ordered only in patients with symptomatic hyperthyroidism.

Imaging Studies

Order triple-contrast CT scan of the abdomen and pelvis to evaluate the extent of disease and the involvement of lymph nodes and other adjacent structures (eg, bowel).
Pelvic sonography is optional if a CT scan has already been performed. Frequently, this is an initial study.
Mammography should be performed in patients with pelvic masses of unknown origin.
Order chest radiographs in indicated patients.
In select cases, preoperative evaluation with uptake of sodium iodide I-123 has been performed to demonstrate thyroid uptake in pelvic masses.

Other Tests

If not current, order a Papanicolaou test.
Iodine-131 scanning
- For masses greater than 5 cm or in patients with suspected struma
- To evaluate active thyroid tissue in the pelvis or abdomen
Order sigmoidoscopy or colonoscopy to evaluate bowel involvement if a triple-contrast CT scan is not available or if bowel involvement is suspected.

Procedures

Thoracentesis
- Perform this procedure in patients with malignant pleural effusion.
- Cytology may reveal adenocarcinoma in the pattern of malignant thyroid cells.

Histologic Findings

Pathological examination reveals thyroid tissue as the major component of the teratoma. Malignant transformation of the thyroid tissue may be papillary, follicular, or mixed pattern, and it can include elements of mucinous cystadenocarcinoma, Brenner tumor, carcinoid, or melanoma. Birefringent crystals of calcium monohydrate are present in most patients, which is considered specific for tumors of thyroid origin. Immunohistochemical staining for thyroglobulin, triiodothyronine (T3), and thyroxine (T4) can confirm the diagnosis. Vascular invasion is rare.

Treatment

Medical Care

Ablation with iodine-131 has been advocated as adjunctive therapy if pathological examination or staging suggests malignant transformation.
Repeat treatment is still therapeutic if recurrence is detected.

Surgical Care

Definitive therapy depends on the extent of preoperative disease and the future childbearing wishes of the patient.

Since most cases are unilateral and benign, simple oophorectomy is appropriate for most patients.
If the contralateral ovary is involved or if the patient has finished childbearing, total hysterectomy with bilateral salpingo-oophorectomy is appropriate.
If evidence of peritoneal metastasis is present, appropriate debulking is indicated. In patients with thyroid involvement, a concomitant thyroidectomy has been advocated.
Preoperative details
- Symptoms of thyroid involvement are rare, thus preoperative thyroid testing or thyroid scanning is unlikely to have occurred.
- Most cases are found incidentally.
Intraoperative details
- Most cases are found as part of a mature teratoma.
- Standard surgical resection is sufficient.
Postoperative details
- Postoperative changes in thyroid function can range from hypothyroidism to thyroid storm.
- Stimulating antibody release has been implicated in hyperthyroid cases.

Follow-up

Further Inpatient Care

For patients with struma occurring in a mature teratoma, standard surgical follow-up care is sufficient.
For patients with malignant transformation and vascular invasion, iodine-131 scanning should be performed to locate active metastases. Thyroidectomy may be considered, and ablation of active thyroid tissue using iodine-131 has been advocated.²

Complications

Significant changes in thyroid function may occur in the immediate perioperative period.

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-131 scanning, and repeat iodine radioablation can lead to extended disease-free survival.
In an analysis of 88 patients with malignant struma ovarii, the overall survival rate for all patients was 89% at 10 years and 84% at 25 years.³

Patient Education

For excellent patient education resources, visit eMedicine's Endocrine System Center. Also, see eMedicine's patient education article Thyroid Problems.

Miscellaneous

Special Concerns

Current controversies revolve around the diagnosis of malignancy, ie, whether to classify the struma using ovarian or thyroid carcinoma criteria.
Because struma ovarii is extremely uncommon, there is no consensus on treatment. Each case must be managed individually.

References

Utsunomiya D, Shiraishi S, Kawanaka K. Struma ovarii coexisting with mucinous cystadenoma detected by radioactive iodine. Clin Nucl Med. 2003;28(9):725-7. [Medline]. [Full Text].
McGill JF, Sturgeon C, Angelos P. Metastatic struma ovarii treated with total thyroidectomy and radioiodine ablation. Endocr Pract. Mar 2009;15(2):167-73. [Medline].
Robboy SJ, Shaco-Levy R, Peng RY, Snyder MJ, Donahue J, Bentley RC, et al. Malignant struma ovarii: an analysis of 88 cases, including 27 with extraovarian spread. Int J Gynecol Pathol. Sep 2009;28(5):405-22. [Medline].
Dardik RB, Dardik M, Westra W. Malignant struma ovarii: two case reports and a review of the literature. Gynecol Oncol. Jun 1999;73(3):447-51. [Medline].
Ihalagama IR, Hewavisenthi SJ, Wijesinghe PS. Pregnancy following treated malignant struma ovarii. Ceylon Med J. Sep 2004;49(3):90-1. [Medline].
Roth LM, Talerman A. The enigma of struma ovarii. Pathology. Feb 2007;39(1):139-46. [Medline].
Yoo SC, Chang KH, Lyu MO, Chang SJ, Ryu HS, Kim HS. Clinical characteristics of struma ovarii. J Gynecol Oncol. Jun 2008;19(2):135-8. [Medline].
Zakhem A, Aftimos G, Kreidy R. Malignant struma ovarii: report of two cases and selected review of the literature. J Surg Oncol. Jan 1990;43(1):61-5. [Medline].

Keywords

teratomatous ovarian tumor, hyperthyroidism, cystadenomas, strumosis, teratoma, pelvic mass, oophorectomy, total hysterectomy, bilateral salpingo-oophorectomy, thyroidectomy

Contributor Information and Disclosures

Author

Bradford W Fenton, MD, PhD, FACOG, Clinical Assistant Professor, Northeast Ohio Universities College of Medicine; Faculty, Obstetrics and Gynecology Residency Training Program, Summa Hospitals Department of Obstetrics and Gynecology; Medical Director, Pelvic Pain Specialty Center
Bradford W Fenton, MD, PhD, FACOG is a member of the following medical societies: American College of Obstetricians and Gynecologists
Disclosure: Nothing to disclose.

Medical Editor

Jordan G Pritzker, MD, MBA, FACOG, Assistant Professor of Obstetrics, Gynecology, and Women's Health, Women's Comprehensive Health Center, Albert Einstein College of Medicine; Physician-In-Charge, Department of Obstetrics and Gynecology, Long Island Jewish Medical Center
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

A David Barnes, MD, PhD, MPH, FACOG, Consulting Staff, Department of Obstetrics and Gynecology, Mammoth Hospital (Mammoth Lakes, California), Pioneer Valley Hospital (Salt Lake City, Utah), Warren General Hospital (Warren, Pennsylvania), and Mountain West Hospital (Tooele, Utah)
A David Barnes, MD, PhD, MPH, FACOG is a member of the following medical societies: American College of Forensic Examiners, American College of Obstetricians and Gynecologists, American Medical Association, Association of Military Surgeons of the US, and Utah Medical Association
Disclosure: Nothing to disclose.

CME Editor

Frederick B Gaupp, MD, Consulting Staff, Department of Family Practice, Hancock Medical Center
Frederick B Gaupp, MD is a member of the following medical societies: American Academy of Family Physicians
Disclosure: Nothing to disclose.

Chief Editor

Michel E Rivlin, MD, Professor, Coordinator of Quality Assurance/Quality Improvement, Department of Obstetrics and Gynecology, University of Mississippi School of Medicine
Michel E Rivlin, MD is a member of the following medical societies: American College of Obstetricians and Gynecologists, American Medical Association, Mississippi State Medical Association, and Royal College of Surgeons of Edinburgh
Disclosure: Nothing to disclose.

Further Reading