Malignant Struma Ovarii Requiring Emergency Surgery for Acut
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A 23-year-old woman was brought to hospital by ambulance because of acute lower abdominal pain that had developed several days previously. Although she had been diagnosed with an ovarian tumor by a local doctor, she had received no specific treatment. She had no remarkable medical or family history.

On admission, pelvic examination revealed an increase in the size of the right adnexa, with marked tenderness on pressure. No abnormalities were found in the uterus or left adnexa. Ultrasonography showed a right ovarian mass measuring 10 cm in diameter. Laboratory examinations, including blood counts and biochemical tests, revealed no significant abnormalities with the exception of an elevated serum C-reactive protein concentration of 8.71 mg/dl. Urgent contrast-enhanced computed tomography showed a tumor measuring 10 cm in diameter in the right ovary. The tumor consisted of a cystic component containing fatty material coexisting with a solid component, and it showed strong contrast enhancement suggestive of bleeding. Based on these findings, torsion of a mature cystic teratoma was suspected (Figure 1), and emergency laparoscopic-assisted tumorectomy was carried out.

On histopathological examination, the resected tumor was lined by epidermoid stratified squamous epithelium and contained glial and cartilage tissues in the cystic part. The solid part was mostly composed of proliferative cells with clear basophilic cytoplasm that were organized into thyroid follicle-like structures (Figure 3). In some areas, the cells formed funicular and solid honeycomb structures. The cells were relatively uniform in size and shape, but they showed an increased nuclear/cytoplasmic ratio; nuclear atypia and evidence of vascular invasion were also found (Figure 4). Immunohistochemical tests showed positive results for anti-thyroid transcription factor 1 antibody and antithyroglobulin antibody, which are thyroid follicle epithelium markers (Figure 5). Based on these histopathological findings, the tumor was diagnosed as malignant struma ovarii containing a poorly differentiated carcinoma component.

Considering the patient’s age, preservation of fertility was attempted. Resection of the adnexa only on the affected side and partial omentectomy were performed at a later date as an additional surgery. At the time of the additional surgery, cytologic examination of the peritoneal washings showed negative results, and the resected tissues showed no evidence of malignancy. The patient showed a favorable postoperative course and was discharged 7 days postoperatively. We explained to the patient and her family that she had a very rare tumor for which there was no established treatment and that a favorable prognosis could be expectable with I131 radiation therapy even if the disease recurred. In deference to the wishes of the patient and her family, the patient was followed at our outpatient clinic without radiation therapy because of concerns regarding the risk of infertility with such therapy. At the time of this writing (12 months after the initial emergency surgery), the patient was still being followed up and had shown no signs of tumor recurrence.