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Struma ovarii: a rare form of presentation and clinical review

2005; Informa; Volume: 84; Issue: 8 Linguagem: Inglês

10.1111/j.0001-6349.2005.0498a.x

1600-0412

Antónia Costa, Ana Margarida Póvoa, M. C. Pires, Vera Paiva, Catarina Pinto, José Martinez‐de‐Oliveira,

Ovarian function and disorders

Mature cystic teratomas represent 40–50% of ovarian neoplasias from which 0.3–1% are struma ovarii, the most common monodermic teratoma of the ovary. Struma ovarii, originally described by von Kalden in 1895, occurs more often in countries where goiter is endemic and has maximum incidence in the fifth decade. It is defined as a teratoma in which thyroid tissue comprises more than 50% of the neoplasic tissue and is classified as benign or malign. The malignant form is rare and is thought to represent 5–37% of the cases, although its criteria of definition have not been uniformly accepted. Most patients are asymptomatic, but they can manifest as abdominal distention, pain, signs and symptoms of urinary or intestinal obstruction, infertility, abnormal uterine bleeding, dysmenorrhea and hot flashes (due to steroid hormone production). Ascites is evident in 1/3 of the cases, but it rarely presents as Meigs' syndrome. In 1/6 of the cases the thyroid gland is augmented. Most benign strumae accumulate iodine and occasionally (5–20%) may even produce significant amounts of thyroid hormones, as they resemble normal thyroid tissue. Strumosis is an entity that is characterized by the surgical findings of peritoneal and omental implants of differentiated thyroid tissue in a patient with benign struma ovarii. It has an indolent clinical course and may result from extraovarian dissemination of a ruptured struma ovarii. The patient was a 69-year-old woman, G3P3, natural menopause at 56 years with no hormone replacement therapy. She had multiple medical conditions including mild mitral and tricuspid insufficiency with normal cardiac function. She was referred to our institution with a 3-month history of 10% weight loss, anorexia and abdominal distension. Physical examination revealed a palpable mass in the lower abdomen. Abdominal ultrasonography showed a heterogeneous mass, ascites and left pleural effusion, and subsequent transvaginal ultrasonography revealed a large complex pelvic mass, 14 cm largest dimension, of probable adnexal origin with neovascularization. A thoracoabdominal computed tomography (CT) scan confirmed these findings. The patient's CA 125 serum level was 72 times greater than the maximum normal level, while her CEA, alpha-fetoprotein, CA 19.9 and CA 15.3 levels were within the normal range. Exploratory laparotomy disclosed 700 cm3 of a yellow-colored ascites and a cystic and solid tumor in the right ovary, 15 cm in largest diameter adherent to the omento and pelvic wall. There were no other surgical findings of clinical interest such as abnormal uterus and left adnexa or evidence of intraperitoneal spread of the disease and retroperitoneal adenopathy. A total hysterectomy and bilateral Salpingo - oophorectomy was performed. A frozen section of the right ovary was interpreted as struma ovarii. Immunohistochemically it stained for thyroglobulin, which confirmed the thyroid epithelial nature of the neoplasm (Fig. 1). The final pathology revealed right benign struma ovarii with cystic and solid components. Cytologic evaluation of the ascitic fluid showed no evidence of malignant cells. In the postoperative period the thyroid function was evaluated with serum thyroid hormone values compatible with hyperthyroidism. Her thyroid gland was not palpable. Cervical ultrasonography showed normal thyroid morphology. Immunohistochemistry of struma ovarii (thyroglobulin positive stain, original magnification × 40). The patient recovered uneventfully and was discharged home on the fourth postoperative day. Three months after her surgery she was doing well, and had partially recovered the lost weight. There was no evidence of ascites or pleural effusion, and the serum thyroid hormone and thyroid stimulating hormone were within the reference ranges, with no need of thyroid suppressives. Our case is a rare form of presentation of a benign struma ovarii. The clinical findings of ascites, hydrothorax, markedly elevated CA 125 and a large complex pelvic mass in a postmenopausal patient strongly suggest pelvic malignancy. Meigs redefined the syndrome that bears his name, 17 years after his initial report, as an association of an ovarian fibroma or a "predominantly fibrous tumor" (including thecoma, granulosa cell tumor, and Brenner tumor), ascites, and unilateral or bilateral pleural effusion, with disappearance of the ascitic fluid and effusion(s) after removal of the ovarian tumor (1). Subsequently, the term Meigs' syndrome has been applied to the same constellation of findings associated with benign pelvic tumor or tumor-like processes, while the term "pseudo-Meigs' syndrome" has been used for cases in which the features of the syndrome are associated with a primary or secondary ovarian cancer and in which the fluid has not been shown to contain malignant cells. The ascitic and pleural fluids in Meigs' and pseudo-Meigs' syndromes are usually serous, but may be serosanguinous. The elevation of CA 125 could have been secondary to the presence of ascites; however, its level was much higher than that typically seen with ascites of benign origin. An ovarian mass and an elevated serum CA 125 level in a postmenopausal woman generally suggest a malignant process. There are studies evaluating the predictive value of CA 125 level and malignancy: values above 35 U/mL are 60% for ovarian cancer and 84% for any type of malignancy (2). Recently, elevations in serum CA 125 have been reported in cases with Meigs' syndrome, but few with markedly elevated CA 125. With the advances in imaging resources a highly probable diagnosis is attained preoperatively. The possibility of struma ovarii should be kept in mind whenever low resistance blood flow within the tumor and free fluid in the pelvis are present in a sonographically appearing mature cystic teratoma (3). Struma ovarii should be included in the differential diagnosis of ovarian tumors when magnetic resonance imaging (MRI) shows a multicystic tumor with a solid component, a multilobulated surface, and signal intensities that indicate the presence of viscid gelatinous material (4). These findings can be corroborated by nuclear medicine methods, specifically iodine scintigraphy and radioimmunoscintigraphy, which reveal a high uptake in the pelvis (5). We now have useful methods for differentiating struma ovarii from other types of ovarian tumors. Diagnosing struma ovarii is less difficult when it is associated with hyperthyroid disease (present in 5–20% of the cases). In our case hyperthyroidism was only diagnosed postoperatively, but reviewing the clinical history the weight loss can probably be attributed to thyrotoxicosis. Because these tumors have their maximum incidence in the fifth decade, perimenopausal age, the hyperthyroid state can mimic climacteric manifestations, leading to underdiagnosing and undertreatment of these situations. It is important to consider struma ovarii in a woman who is proposed for laparotomy because a hyperthyroid crisis can occur after by the surgical aggression, and the thyroid gland can increase in size or hypothyroidism can be installed after oophorectomy, facts that can have serious clinical implications. With this in mind a reduction in morbimortality can be expected by the correct diagnosis and prompt treatment in these situations. In conclusion, benign ovarian tumors can mimic malignant neoplasias. At present, imaging characteristics revealed by ultrasonography and MRI can be highly suggestive of struma ovarii and these can be corroborated by nuclear medicine. Although the preoperative suspicion of struma ovarii does not change the surgical attitude, it can modify and alert the clinician to the appropriate perioperative care of these patients, thereby diminishing their morbimortality.