AACE Clinical Case Reports (Jul 2024)

Pulmonary Metastatic Follicular Thyroid Carcinoma Without Intrathyroidal Primary Thyroid Cancer

  • Sima Saberi, MD,
  • Nicholas Burris, MD,
  • Ka Kit Wong, MBBS,
  • Noah A. Brown, MD,
  • Thomas Giordano, MD, PhD,
  • Nazanene H. Esfandiari, MD

Journal volume & issue
Vol. 10, no. 4
pp. 123 – 126

Abstract

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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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