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Updated: Jun 18, 2025

Spontaneous Murine Model of Anaplastic Thyroid Cancer
Published on: February 3, 2023
Pulmonary Metastatic Follicular Thyroid Carcinoma Without Intrathyroidal Primary Thyroid Cancer
Sima Saberi1, Nicholas Burris2, Ka Kit Wong2
1Division of Metabolism Endocrinology and Diabetes, University of Michigan, Ann Arbor, Michigan.
Background/Objective:
Follicular thyroid cancer without an intrathyroidal primary cancer is rare. We present a patient with multifocal pulmonary metastatic follicular thyroid cancer without apparent cancer within her thyroid.
Case Report:
A 44-year-old woman was referred to the thyroid cancer clinic via telemedicine for evaluation of intrapulmonary thyroid tissue. Her past medical history included Roux-en-Y gastric bypass and hysterectomy with bilateral oophorectomy. Six months prior, abdominal computed tomography (CT) showed incidental bilateral lung nodules. Chest CT demonstrated 4 solid left and 1 solid right lung nodules. Lung nodule core biopsy revealed benign thyroid tissue. Thyroid ultrasound showed bilateral subcentimeter anechoic nodules. Chest CT 6 months after initial CT demonstrated stable lung nodules. The levels of thyroid-stimulating hormone, serum thyroglobulin, and thyroglobulin antibody were 1.63 mIU/L (reference range, 0.3-5.5 mIU/L), 40.9 ng/mL (reference range, 0-35 ng/mL), and <1 IU/mL (reference range, <4), respectively. Positron emission tomography/CT showed fluorodeoxyglucose-avid lung lesions measuring 1.5, 1.1, and 2.2 cm and other subcentimeter pulmonary nodules. Repeat lung core biopsy showed thyroid tissue with microfollicular architecture, favoring metastatic follicular carcinoma with neuroblastoma-RAS gene (NRAS) mutation. Total thyroidectomy performed showed multinodular hyperplasia without thyroid cancer. Her postoperative radioiodine scan demonstrated bilateral iodine-avid pulmonary nodules, a serum thyroglobulin level of 179.8 ng/mL, a thyroid-stimulating hormone level of 151.3 mIU/L, and undetectable serum thyroglobulin antibody. She received 261 mCi of radioactive iodine. Fourteen months later, chest CT revealed decreased lung nodules and a serum thyroglobulin level of 0.7 ng/mL.
Discussion:
Approximately 2 cases of multifocal pulmonary follicular thyroid cancer without a primary source and no other site of metastasis have been reported.
Conclusion:
Pulmonary follicular thyroid cancer without a primary source and no other site of metastasis is extremely rare.
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