A 73-year-old male with a history of small cell lung cancer with metastases to the brain and left adrenal gland was admitted for progressive fatigue and dysphagia. Physical examination disclosed a non-tender thyroid gland that was diffusely enlarged, roughly twice normal size. Laboratory studies revealed a thyroid-stimulating hormone (TSH) of <0.01 and a free thyroxine (free T4) of 2.04. Thyroid ultrasound showed multiple thyroid nodules; the largest was in the right thyroid and measured 2.0 x 1.8 x 2.5 cm. A radioactive iodine uptake test was not done, as the patient had recently received iodinated contrast for a computed tomography scan. Ultrasound-guided fine-needle aspiration cytology of the largest thyroid nodule demonstrated malignant cells consistent with small cell carcinoma, similar in morphology to that in the patient’s previous lung mass and metastatic left adrenal biopsies. Based on these findings, the diagnosis of metastasis from small cell carcinoma of the lung was made. Although the patient did not have any signs or symptoms of hyperthyroidism, he was started on methimazole while awaiting more definitive treatment. Unfortunately the patient’s condition rapidly deteriorated, and he was determined not to be a candidate for further chemotherapy or radiation therapy. The patient ultimately decided on comfort care and was discharged to hospice.
Metastatic spread to the thyroid gland is rare, representing only 1.4-3% of all thyroid cancers. Although the thyroid gland has a rich vascular supply, it has been postulated that the fast flow of blood through the gland reduces the likelihood of metastatic deposits. The majority of patients are euthyroid at presentation, with hyperthyroidism seen less commonly. When it does occur it is thought to be due to hormone leakage from the gland as a result of neoplastic damage. This patient had bronchogenic carcinoma of the small-cell type, which has rarely been reported to metastasize to the thyroid. It is conjectured that the aggressive and rapid development of the neoplasm often renders any metastasis to the thyroid clinically subtle. As a result, thyroid lesions representing metastases may be easily overlooked because the physician’s attention is directed to more clinically significant lesions elsewhere. Although detection of metastasis to the thyroid gland often portends a poor prognosis, it has been reported that aggressive medical and surgical management may be effective in a small percentage of patients.
Hospitalists frequently encounter thyroid nodules in clinical practice. In any patient with a history of malignancy presenting with a new thyroid mass, metastatic disease should be suspected. The diagnosis is made with fine-needle aspiration cytology.
To cite this abstract:Chung R, Patham B, Sharma M. When Lung Meets Thyroid: An Unusual Site for Metastasis. Abstract published at Hospital Medicine 2015, March 29-April 1, National Harbor, Md. Abstract 488. Journal of Hospital Medicine. 2015; 10 (suppl 2). https://www.shmabstracts.com/abstract/when-lung-meets-thyroid-an-unusual-site-for-metastasis/. Accessed January 19, 2020.