Struma Ovarii Workup

• CBC count
• Blood type and screen
• Cancer antigen 125

  • Nonspecific marker elevated in a variety of benign clinical settings, including menstruation, pregnancy, endometriosis
  • Elevated in epithelial ovarian, endometrial, bowel, breast, and lung cancer
  • Elevated in only 8 cases reported in the literature in the setting of struma ovarii^[6]
• Thyroid function tests are ordered only in patients with symptomatic hyperthyroidism.

• In a review of 12 cases, Shen et al found that CT and MRI appearance of these tumors may be helpful diagnostic features.^[7]
• Triple-contrast CT scan of the abdomen and pelvis should be performed to evaluate the extent of disease and the involvement of lymph nodes and other adjacent structures (eg, bowel). Typically, struma ovarii appear as a multicystic mass with no or moderate cystic wall enhancement.^[8]
• If a triple-contrast CT scan is not available and bowel involvement is suspected, sigmoidoscopy or colonoscopy should be performed.
• 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.
• Chest radiographs should be obtained 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.

• Papanicolaou test
• Iodine-123 scanning (In patients with suspected struma, this will evaluate active thyroid tissue in the pelvis or abdomen.)
• Thoracentesis in patients with pleural effusion (Cytology may reveal adenocarcinoma in the pattern of malignant thyroid cells.)

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 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.

Pathological examination reveals thyroid tissue as the major component of the mass, and is most commonly found in a teratoma. 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.

Malignancy is defined by histological features of the tumor including cellular atypia and hyperplasia, nuclear pleomorphism, mitotic activity, and invasion into surrounding vessels or the ovarian capsule. Currently, the pathological criteria used in diagnosing thyroid carcinoma are widely accepted as the standard in diagnosing malignant struma ovarii.^[4] However, there is still controversy over the defining characteristics of a malignant struma ovarii tumor. A blinded analysis of 19 histologic characteristics of thyroid tumors in 60 clinically benign and 26 clinically malignant struma ovarii cases found the majority of characteristics to be similar in both types of tumors. The clinical outcome of struma ovarii is unpredictable and cannot be predicted based on histologic features.^[9]

Malignant struma ovarii is divided into 3 different categories by histology.

• Papillary type is the most common and identified by “ground glass” or overlapping nuclei
• The follicular variant of papillary carcinoma shares the same nuclear characteristics as the papillary type but has a follicular architecture.
• Follicular carcinoma is identified by follicles of mitosis around vascular and capsular structures.^[10]