Malignant struma ovarii with a robust response to radioactive iodine

A Case of Solid-Appearing Struma Ovarii: Pitfall in the Assessment Using Ovarian-Adnexal Reporting and Data System Magnetic Resonance Imaging Score

Struma ovarii is a monodermal teratoma characterized by the presence of >50% thyroid tissue. It is mostly benign; therefore, preoperative diagnosis is important. It usually manifests as a multilocular cystic mass but rarely as a predominantly solid mass. On magnetic resonance imaging (MRI), solid-appearing struma ovarii showed early signal intensity enhancement on dynamic gadolinium-enhanced T1-weighted images, which histopathologically indicates the presence of thyroid tissue with abundant blood vessels. The Ovarian-Adnexal Reporting and Data System (O-RADS) MRI score is a validated classification worldwide for characterizing adnexal lesions. Based on the morphology, signal intensity, and enhancement of any solid tissue on the MRI, the scoring system can be used to classify adnexal lesions into five categories from score one (no adnexal mass) to score five (high risk of malignancy). An adnexal solid mass with a higher signal intensity than that of the myometrium 30-40 seconds after gadolinium (Gd) injection on non-dynamic contrast-enhanced (non-DCE) MRI was assigned a score of 5 (high risk of malignancy).  We present a case of solid-appearing struma ovarii with a higher signal intensity than that of the myometrium 30 seconds after Gd injection on non-DCE MRI, and it was classified as score five preoperatively. Therefore, a total abdominal hysterectomy with bilateral salpingo-oophorectomy was performed despite the presence of a benign ovarian mass. When an adnexal mass with a higher signal intensity than that of the myometrium 30-40 seconds after Gd injection on non-DCE MRI is encountered, struma ovarii should be included in the differential diagnosis, despite the O-RADS MRI score of five and management of the situation should be discussed.

Clinical use of thyroglobulin: not only thyroid cancer

Thyroglobulin (TG) is a dimeric glycoprotein produced exclusively by mature thyroid tissue and stored within the follicular lumen. It is essential for the organification of iodine and the production of thyroid hormones. The concentration of TG in the bloodstream varies between individuals and depends on factors such as thyroid mass, stimulation of the gland by thyrotropin or autoantibodies, and tissue destruction. TG is essential to monitor patients with differentiated thyroid cancer; however, its use is not limited only to this clinical entity. Measurement of circulating TG can provide better insight into numerous clinical scenarios, such as destructive thyroiditis, presence of ectopic thyroid tissue, thyroid trauma, factitious thyrotoxicosis, or iodine nutrition. Lately, TG has found its new clinical use in immune checkpoint-related thyroid dysfunction. TG measurement should be performed carefully in patients with antithyroglobulin antibodies due to possible laboratory interferences. In this review, we offer a summary of current knowledge about the clinical use of TG and the implications it brings to daily practice.

Papillary follicular variant thyroid cancer in a malignant struma ovarii: a report of a rare case

Summary

A 33-year-old female presented in 2013 with left flank pain. Ultrasound and MRI pelvis showed a complex mass 9 × 7 cm arising from the left ovary suggestive of ovarian torsion. She underwent a laparoscopic cystectomy, but the patient was lost to follow-up. Three years later, she presented with abdominal distension. Ultrasound and CT scan revealed a solid left ovarian mass with ascites and multiple peritoneal metastasis. Investigations showed elevated CA 125, CA 19-9. Ovarian malignancy was suspected. She underwent total abdominal hysterectomy and bilateral salpingo-oophorectomy on November 2016. The histopathology confirmed a well-differentiated thyroid cancer of ovarian origin with features of a papillary follicular variant without evidence of ovarian cancer and the thyroglobulin (Tg) level was elevated, more than 400 consistent with the diagnosis of malignant struma ovarii. The follow-up post-surgery showed normalization of CA 125, CA 19-9 and Tg. The patient underwent total thyroidectomy on January 2017. The histology was benign excluding thyroid cancer metastases to the ovary. She was started on thyroxine suppression, following which she received two ablation doses 131iodine (131I) each 5.3 GBq. The Tg remains slightly elevated at less than 10. 131I WBS showed no residual neck uptake and no distant avid metastasis. She was planned for molecular analysis which may indicate disease severity. We describe a case of malignant struma ovarii with widespread metastatic dissemination and a good response to surgery and 131I treatment without recurrence after 5 years of follow-up. The Tg remains slightly elevated indicating minimal stable residual disease.

Learning points

Malignant struma ovarii is a rare disease; diagnosis is difficult and management is not well defined. Presentation may mimic advanced carcinoma of the ovary. Predominant sites of metastasis are adjacent pelvic structures. Thyroidectomy and 131iodine therapy should be considered. The management should be similar to that of metastatic thyroid cancer.

The Clinical and Pathological Characteristics of Malignant Struma Ovarii: An Analysis of 144 Published Patients

The objective of this study is to summarize the clinical and pathologic characteristics of malignant struma ovarii to facilitate the early diagnosis and treatment of this disease. All 144 patients were females from 27 countries. The mean age of the patients at diagnosis was 42.6 years. Overall, 35.71% of the patients underwent unilateral oophorectomy, 58.57% of the patients underwent bilateral oophorectomy, 5.72% of the patients were not ovariectomized, and 38.57% of the patients received radioactive iodine treatment with an average dose of 158.22 mCI each time. “Impure” types accounted for 70.19% of the cases, while pure types accounted for 29.81% of the cases. Among these cases, papillary thyroid carcinoma accounted for 50.00%, follicular thyroid carcinoma accounted for 26.47%, follicular variant of papillary thyroid carcinoma accounted for 18.63%, papillary and follicular mixed thyroid carcinoma accounted for 2.94%, anaplastic carcinoma accounted for 0.98%, and medullary carcinoma accounted for 0.98%. In total, 21 patients (51.22%) had elevated CA125. More than half of the patients (51.94%) had metastasis outside the ovary. The most common metastatic site was the pelvic cavity. The misdiagnosis rate was 17.27%. Mortality was related to metastasis and the cancer type. Gene mutations were found in the NRAS, KRAS, BRAF, and KIT genes and were similar to those in thyroid carcinoma, but some patients (37.5%) did not exhibit any gene mutations. Regardless of the treatment received, the survival rate is high. Treatment could initially include ovariectomy; however, in cases with metastasis and iodine uptake of the metastatic tumor, thyroidectomy, radioactive iodine therapy, and thyroid hormone inhibiting therapy are indicated.