Struma ovarii: a rare benign pathology which may erroneously suggest malignancy

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The presence of a pelvic mass with suspicious clinical and sonographic features associated with elevated levels of CA 125 may be suggestive of gynecological malignancy even in fertile women. However, there are benign conditions of the ovaries and uterus that are associated with increased concentrations of serum CA 125. Some of these conditions show an altered sonographic pattern and can mimic pelvic cancer. One such condition is struma ovarii which may lead to suspicion of an ovarian malignancy since all the signs are present. A 31-year-old woman was admitted to the Institute of Gynecology of Messina University in September 1998. Four weeks prior to referral, she had undergone a voluntary termination of pregnancy. An ultrasound scan performed on that occasion revealed a pelvic mass with a diameter of a few centimeters. At admission, she complained of a slight lower abdominal pain and pelvic examination revealed a tender mass in the left adnexal region with a quite normal sized uterus. No symptoms or clinical signs that might suggest thyroid hormone imbalance were present. An ultrasound scan revealed that the uterus and the right ovary were normal in size and morphology; in the left adnexal region there was an 11 cm solid/cystic mass. MRI confirmed ‘the presence of a 10×11×9 cm pelvic mass in L5-S1scan showing a nodular component with necrotic features and some small calcifications.’ Free fluid was present. The detection of serum CA 125 levels showed a value of 689 U/ml. The other hematological and biochemical tests were normal and a chest X-ray was negative. Some days later the patient underwent laparotomy. At operation about 300 ml of ascitic fluid was drained off and then submitted for cytological analysis. An irregular cystic mass in the left ovary measuring 10×9 cm was found. The tumor was removed through a salpingo-oophorectomy and sent for frozen section assessment. All abdominal and pelvic organs were examined and the results were normal. The frozen section reported a benign multicystic lesion with thyroid tissue (struma ovarii) (Fig. 1). The ascitic fluid was negative for malignant cells, and pathology confirmed a benign struma of the left ovary. Present ovarian lesion. Architectural pattern of a ‘struma ovarii’ inside which are patent by both large and small thyroid follicles. These contain colloid-like material while an inflammatory infiltrate occurs everywhere in the interstitium (H.E. original magnification ×125). Post-operative recovery was uneventful. Serum CA 125 levels decreased to 52 U/ml three days after surgery and returned to normal after a week. Thyroid function tests performed only after surgery were within normal limits. The patient was discharged after 7 days. Struma ovarii is a rare benign tumor of the ovary. Although thyroid elements have been described in almost 20% of the cases of dermoid cysts, the term ‘struma’ is used when the thyroid tissue constitutes more than 50% of the tumor (1). Struma ovarii usually presents itself with abdominal and pelvic symptoms of a mass. In some cases it can develop ascites and hydrothorax (pseudo-Meigs syndrome), and in a small percentage an endocrinological activity may be present (2, 3). Recently, some authors have reported cases of struma ovarii associated with ascites, pleural effusions and elevated serum CA 125 levels (1, 4). Our case shows analogies with the few cases reported in the literature (1-3). It differs in some important respects. Firstly the patient’s age, which is much lower than that when the majority of these tumors occur i.e. in the fifties. Our patient’s desire to preserve fertility raised an additional problem, as the few cases reported in the literature concern postmenopausal women who had no need of a planned conservative surgery. Secondly, the growth of the pelvic mass was rather swift, probably due to the concomitant initial pregnancy. Thirdly, the absence of pleural effusion, in our opinion, was due to the early diagnosis and timely treatment. Finally, this clinical report emphasizes that there are benign gynecological conditions which may manifest themselves in different ways and may show clinical, ultrasonographic and biochemical signs suggestive of malignancy (5, 6). For these reasons it is wise to behave with caution in the assessment of pelvic masses, particularly in patients of fertile age who wish to preserve their fertility.