Missed Initial Diagnosis of Malignant Struma Ovarii Containing Follicular Thyroid Carcinoma

Abstract

Distant metastasis of rare malignant struma ovarii (MSO) has been reported for cases associated with papillary thyroid cancer but few with follicular thyroid cancer. A 38-yr-old woman with struma ovarii that was initially diagnosed as "benign" presented with pulmonary metastasis and coughing 17 yr later. The lungs lesions were confirmed to be follicular thyroid cancer by biopsy. Rereview of the initial surgical ovary specimens confirmed the condition to be MSO with follicular thyroid cancer. The patient was treated with total thyroidectomy, which showed no thyroid malignancy, followed by (131)I (iodine-131) treatments. Dramatic reduction was observed in both the stimulated thyroglobulin level and the size of the pulmonary metastases over 1 yr. During the following 3-yr follow-up, the patient remained clinically well, with undetectable thyroglobulin (<1 ng/mL) and small stable pulmonary lesions. This is an exceedingly rare case of MSO with follicular thyroid cancer metastasized to the lungs presenting with a late onset but a fortunate excellent response to multidiscipline treatments. It is advisable that struma ovarii be carefully examined to avoid missing malignancy and patients be clinically followed up even with a benign initial diagnosis.

Follicular carcinoma originating from struma ovarii: A case report

“…[4] As with other ovarian malignancies, these lesions can migrate to the pelvic or abdominal lymph nodes through the lymphatic system, and can be directly implanted in the greater omentum, abdominal cavity, and transferred to the bone, brain, lung, and liver. [7,8] Since follicular carcinoma originating from ovarian goiter and thyroid follicular carcinoma have similar molecular genetic abnormalities, the histological morphology of the 2 is similar. Gene alterations in follicular thyroid carcinoma include point mutations in HRAS, NRAS, and KRAS genes.…”

Highly Differentiated Follicular Carcinoma of Ovarian Origin: A Systematic Review of the Literature

“…Despite the morphologically benign characteristics of the disease, dissemination of the tumor is required in order to establish the diagnosis of HDFCO [ 7 , 32 ]. As presented in the literature, some of the patients even presented with bone, live, lung, or heart metastases [ 17 , 21 , 34 ]. Thereafter, considering that ovarian struma is a neoplasm, and not a goiter as seen in the thyroid, its dissemination and metastatic potential to other organs reinforces the view, as cited in the last 2020 WHO classification of female genital tumors, that “the presence of peritoneal implants of well differentiated thyroid tissue in a patient with histologically benign struma ovarii known as strumosis, is now thought to represent metastasis from a highly differentiated follicular carcinoma arising in struma ovarii” [ 7 ].…”