An Unusual Case of Malignant Struma Ovarii Causing Thyrotoxicosis

Abstract

Background: Struma ovarii (SO) is a specialized monodermal teratoma predominantly composed of mature thyroid tissue, accounting for approximately 5% of all ovarian teratomas. Thyrotoxicosis is seen in about 8% of patients with SO. Most SO cases are benign with only 5-10% being malignant, and malignant SO causing thyrotoxicosis is very uncommon. Case: A 64-year-old woman had been diagnosed with thyrotoxicosis 2 years previously. The thyroid gland was palpable with a micronodular texture, and the patient was euthyroid under carbimazole. She presented with abdominal pain and progressive enlargement of the abdomen over a 2-month period. An abdominal ultrasonography revealed a pelvic mass and a large fluid collection. Additional imaging confirmed the presence of a complex right ovarian mass measuring 13 cm. The patient underwent a total abdominal hysterectomy and bilateral salpingo-oophorectomy, omentectomy and appendectomy. The histological examination revealed the presence of ‘follicular thyroid-type carcinoma arising in an SO of the right ovary, with metastatic infiltration in the tissue fragments from the pouch of Douglas'. Antithyroid treatment was discontinued 1 month after surgery in light of the pathology result. During the 4-year follow-up, the patient remained euthyroid. Conclusion: There has been controversy about the management of malignant SO, which is a rare entity. Malignant SO causing thyrotoxicosis is even more uncommon. As clinical signs are nonspecific, other causes of thyrotoxicosis must be considered for a differential diagnosis. Our case is one of the very few cases ever reported.

Malignant Thyroid-type Papillary Neoplasm in Struma Ovarii: A Case Report

“…The majority of ovarian germ cell tumors are benign, of whom mature teratomas make up 15-20% of the cases [2]. In comparison to its benign counterpart, the incidence of malignant ovarian germ cell tumors is small [1,3]. Teratoma is a subtype of germ cell tumor that arises from one or more of the three germ cell layers.…”

“…An estimated 15% of teratomas are known to contain thyroid tissue [2]. SO is a monodermal ovarian teratoma, whose architecture is composed of more than 50% of thyroid tissue [3,6]. It contributes to approximately 2-3% of all ovarian tumors and 2-5% of all ovarian teratomas [1][2][3][4].…”

“…SO is a monodermal ovarian teratoma, whose architecture is composed of more than 50% of thyroid tissue [3,6]. It contributes to approximately 2-3% of all ovarian tumors and 2-5% of all ovarian teratomas [1][2][3][4]. The incidence of SO is higher in older adults, although it has also been reported in younger women [7].…”

“…It presents more frequently between the ages of 40 and 60 [1]. The majority of SO are benign and belong to the category of mature teratomas, which account for 2-5% of overall benign mature teratomas [2,3]. Rarely, a malignant type of tissue may arise in the background of SO, thereby transforming it into a thyroid-type carcinoma.…”

“…Rarely, a malignant type of tissue may arise in the background of SO, thereby transforming it into a thyroid-type carcinoma. In such malignant cases, the most common histological subtypes, in the order of decreasing prevalence, include papillary thyroid carcinoma (PTC), follicular thyroid carcinoma, and highly differentiated follicular carcinoma (HDFCO) [3]. Malignant struma ovarii (MSO) are usually asymptomatic.…”