Struma ovarii is an infrequent type of dermoid ovarian tumor that is usually benign and composed of at least 50% thyroid tissue. It may be part of a teratoma or cystadenoma and may also have a malignant character (papillary thyroid carcinoma). Thyroid tissue may be also found in the peritoneal cavity as in benign strumosis. In strumal carcinoid, the carcinoid tissue is present in the struma ovarii.
Struma ovarii patients, often aged 40 to 60, more frequently present with ovarian, rather than thyroid hyperfunction complaints . Ovarian symptoms include metrorrhagia, abdominal or pelvic pain or palpable abdominal mass that has no specific traits on clinical examination, making diagnosis difficult. All these signs are nonspecific and overlap with those caused by an ovarian malignancy. Abnormal liquid accumulation like ascites  (leading to the presence of a positive fluid wave test) and hydrothorax with ascites (leading to crackles on pulmonary auscultation and dyspnea), known as the pseudo-Meigs syndrome may also be encountered. Ascites occurs in 17 to 33% of patients  and may spontaneously disappear after tumor excision. Thyroid tumors may also be present . Struma ovarii may be completely asymptomatic  and discovered on pelvic imaging studies or surgery performed for other complaints . Hyperthyroidism signs are present in 5 to 8% of patients  . Some of the women affected by the condition also have a goiter  due to Graves' disease .
Struma ovarii diagnosis is aided by blood workup and imaging modalities. Aside from complete blood cell count, the cancer antigen, although non-specific, may sometimes be useful . However, its presence does not necessarily signify struma ovarii is present, as it is elevated in numerous other physiological and pathological instances. Although hyperthyroidism symptoms may be absent, the serum thyroid-stimulating hormone may be low and free thyroxine and/or triiodothyronine levels may be increased. However, they are not commonly ordered if increased thyroid function signs are absent. Also, despite the fact that clinical examination usually does not describe an enlarged thyroid, serum thyroglobulin level may be increased.
In the attempt to characterize the nature of the pelvic tumor, several methods may be applied. Pelvic ultrasound is usually the first study performed and offers limited information. Triple-contrast computed tomography (CT) scan describes the cystic aspect of the pathological mass and evaluates if lymph nodes and neighboring structures are also implicated . Thoracic radiography is used when lung metastasis or hydrothorax are suspected. If pleural effusion is present, a diagnostic puncture may be useful. Fluid is evaluated to rule out adenocarcinoma. The true thyroid glandular nature of the tumor is highlighted by the sodium iodide I-123 uptake of the pelvic tumor.
After excision, strumal tissue is examined in order to determine if it is malignant or benign. Malignancy is suggested by cellular hyperplasia and atypia, increased mitotic activity, and invasion of underlying structures and consists of thyroid carcinoma or stromal carcinoid . However, there seems to be a thin line between malignant and benign cases concerning histology traits, therefore the end result of therapy cannot be predicted by this method . However, carcinoid variant, even if present, is usually not aggressive and cured by surgical excision . Metastasis can be found in the mesentery, brain, liver, bone, contralateral ovary, peritoneum or lungs.