7639 A Rare Cause of Lung Adenocarcinoma with Metastasis to the Thyroid

Abstract Disclosure: E. Echevarria-Torres: None. C.G. Yap: None. K.E. Izuora: None. A rare cause of lung adenocarcinoma with metastasis to the thyroid. Metastasis to the thyroid gland from non-thyroid malignancies is rare. When metastasis occurs, presenting symptoms are typically nonspecific, representing a diagnostic challenge. With the goal of raising awareness, we present a case of lung adenocarcinoma with metastasis to the thyroid. An 85-year-old man with a history of hypertension, hyperlipidemia and 60 years smoking history presented to the endocrine clinic for evaluation of subclinical hyperthyroidism. On the physical exam, there was fullness in the right thyroid area which on ultrasound showing a large right thyroid nodule occupying the entire lobe. There was also a solid 4.5 cm x 3.4 cm x 4.6 cm nodule in the mid-anterior left thyroid lobe. Fine needle aspiration cytology of right nodule revealed malignant cells and cell block material positive for TTF-1 (Thyroid Transcription Factor 1) concerning for malignancy. The left thyroid nodule cytology was consistent with benign follicular nodule. Chest CT ordered for surgical planning showed right upper lobe pleural-based lung opacity measuring 3.7 cm x 2.9 cm with supra clavicular lymphadenopathy. Biopsy of lung mass and supra clavicular lymph nodes revealed primary lung adenocarcinoma involving the lymph nodes consistent with stage Iva (cT3NxM1b). The patient was referred to oncology for further management. Discussion: Metastatic lesions to the thyroid gland account for less than 1 % of all malignant thyroid tumors with most cases found on autopsy. This is hypothesized to be due to the rich blood supply and high iodine content of the thyroid gland. Thyroid metastasis usually presents several years after initial diagnosis and treatment of non- thyroid malignancy. Patients can present with enlarging thyroid nodules, neck swelling, dysphagia and, in rare instances, upper airway obstruction. We present a rare case of lung cancer with metastasis into the thyroid. The thyroid nodule initially palpated upon physical exam led to eventual thyroid ultrasound and subsequently to his diagnosis of lung adenocarcinoma after findings of lung nodule which was biopsied and showed primary lung adenocarcinoma. TTF-1 was also positive which is typically expressed by lung adenocarcinomas. Treatment for thyroid metastasis is surgery, along with treatment of primary malignancy. The earlier the diagnosis and treatment the more favorable the prognosis. Radiotherapy and chemotherapy are other means to reduce the recurrence. Thyroid hormone replacement will be warranted post operatively for hypothyroidism. We present this uncommon case to raise awareness about the presentation of thyroid metastasis to enhance timely diagnosis and intervention. Presentation: 6/1/2024