Management of malignant struma ovarii: is aggressive therapy justified? Case report and literature review

Abstract

Background: Struma ovarii (SO) is a rare ovarian teratoma containing predominantly thyroid tissue. In rare situations SO may develop malignancy. Most cases of malignant struma ovarii (MSO) are diagnosed after surgical removal, based on histopathological examination. There are still controversies regarding the extent of surgery and postoperative management in MSO, due to its unpredictable behavior, possible risk of metastasis and relatively high rate of recurrence.

Case presentation: We present the case of a patient diagnosed with a right ovarian cyst discovered incidentally during routine ultrasound examination. Its rapid growth and pelvic MRI raised the suspicion of a neoplastic process. She underwent total hysterectomy and bilateral adnexectomy. The anatomopathological diagnosis was MSO with follicular variant of papillary thyroid carcinoma. Prophylactic total thyroidectomy was performed, followed by radioactive iodine ablation (RAI), and suppressive therapy with levothyroxine. At 1 year follow-up, the patient was disease free.

Conclusions: Even if latest literature reports consider that completion of local surgery with total thyroidectomy and RAI might be too aggressive in cases of MSO without extraovarian extension, in our case it was decided to follow the protocol for primary thyroid carcinoma, in order to reduce the recurrence risk.

Keywords: Malignant struma ovarii; Radioactive iodine ablation; Surgery; Teratoma; Thyroid carcinoma.

Fig. 1

Pelvic MRI showing right adnexal mass with median development, mixed predominantly cystic structure, multiloculated, multiseptated, with reduced solid component, with dimensions of 79 × 66x72 mm (white arrow); a. Coronal MRI: T1-weighted image showing variable signal intensity for the cystic component (high and intermediate), and intermediate signal intensity for the solid component of SO; b. Sagittal MRI: T2-weighted image showing high signal intensity for the cystic component and low signal intensity for the solid component (septations and walls)

Fig. 2

Follicles with variable dimensions, covered by one layer of cells, filled with colloid (HE, × 40). HE = Haematoxylin and eosin staining

Fig. 3

Area with malignant changes (center of the image), with predominantly follicular pattern, isolated papillae and clear, vesicular nuclei specific for papillary malignant tumor (HE, × 100). HE = Haematoxylin and eosin staining

Fig. 4

Clear, vesicular nuclei specific for papillary malignant tumor and isolated mitoses (HE, × 400). HE = Haematoxylin and eosin staining

Fig. 5

Diffuse, strong nuclear positivity at immunohistochemical staining for TTF1, consistent with the diagnosis of ovarian thyroid tissue (TTF1, × 10). HE = Haematoxylin and eosin staining

Fig. 6

Post-therapeutic I-131 whole body scan – anterior view (left) and posterior view (right). Remnant uptake in the pelvic area after iodine radiopharmaceutical washout (black arrows)