MALIGNANT STRUMA OVARII IN A PATIENT WITH GRAVES’ DISEASE

A CASE REPORT

Abstract

INTRODUCTION/BACKGROUND
Malignant struma ovarii (MSO) is a rare ovarian teratoma containing malignant thyroid tissue, accounting for <5% of all struma ovarii cases. Papillary carcinoma is the most common histological subtype, followed by follicular carcinoma. Diagnosis may be challenging, especially when coexisting with thyroid nodules or autoimmune thyroid diseases such as Graves’ disease, due to overlapping histologic and functional features.

CASE
A 58-year-old female with longstanding hyperthyroidism due to Graves’ disease presented with an abdominal mass measuring 15 × 10 × 9 cm. Laparotomy in September 2023 revealed a right ovarian tumor. Histopathology showed adenomatous struma with focal atypia. Immunohistochemistry revealed BRAF V600E positivity with partial CD56 and CK19 expression, and negative HBME1 and cyclin D1. Although non-classical, this staining pattern can be observed in thyroid carcinoma with oncocytic or clear cell features.

Thyroid ultrasound showed a bilateral multinodular goiter with a TIRADS 4 nodule; FNAB was benign. A thyroid scan revealed diffusely increased uptake (55.3%), and elevated TRAb (4.43 IU/L), consistent with Graves’ disease. Total thyroidectomy in June 2024 revealed adenomatous struma with chronic inflammation and no malignancy, likely representing a degenerating nodule in the context of treated Graves’ disease.

This case highlights the complexity of diagnosing MSO in the setting of autoimmune thyroid disease. Total thyroidectomy was performed to exclude primary thyroid carcinoma and to support future surveillance or radioactive iodine therapy.

CONCLUSION
MSO should be considered when ovarian tumors contain thyroid tissue with atypia. In patients with Graves’ disease, degenerating thyroid nodules may mimic malignancy. A multidisciplinary approach using imaging, histopathology, immunohistochemistry, and autoantibody testing is essential for accurate diagnosis and long-term management.