title: 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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Endocrinology, Alexandra General Hospital, Athens, Greece.
authors.forename: Elli
authors.initials: E
authors.lastname: Anagnostou
authors.affiliation: Department of Endocrinology, Alexandra General Hospital, Athens, Greece.
authors.forename: Antonios
authors.initials: A
authors.lastname: Polymeris
authors.affiliation: Department of Pathology, Alexandra General Hospital, Athens, Greece.
authors.forename: Georgios
authors.initials: G
authors.lastname: Morphopoulos
authors.affiliation: Department of Endocrinology, Alexandra General Hospital, Athens, Greece.
authors.forename: Alexios
authors.initials: A
authors.lastname: Travlos
authors.affiliation: Department of Endocrinology, Alexandra General Hospital, Athens, Greece.
authors.forename: Vassiliki
authors.initials: V
authors.lastname: Sarantopoulou
authors.affiliation: Department of Pathology, Alexandra General Hospital, Athens, Greece.
authors.forename: Irini
authors.initials: I
authors.lastname: Papaspyrou
keywords: Follicular carcinoma; Malignant struma; Ovarian tumor; Struma ovarii; Teratoma; Thyrotoxicosis