Metastatic squamous cell carcinoma of the lung to the thyroid gland presented as nodular goiter: a rare case report

Metastasis of squamous cell lung carcinoma to the thyroid gland is an extremely rare event. It frequently metastasizes to lymph nodes, liver, adrenal glands, bone, brain, and pleura. Among the lung carcinomas metastasizing to the thyroid, adenocarcinomas are the most common followed by squamous cell carcinomas (SCCs). CASE PRESENTATION: A 58-year-old male patient presented with bilateral neck swelling. Fine needle aspiration is performed and was undetermined. Ultrasonography of the neck demonstrated multiple hypoechoic nodules with thyroid enlargement. The patient was diagnosed with nodular goitre and he underwent a total thyroidectomy. Microscopically, the Hematoxylin and eosin-stained sections revealed thyroid follicles with sheets composed of polygonal cells with pleomorphic nuclei, prominent nucleoli, and a moderate amount of eosinophilic cytoplasm. Keratin pearls were present. Based on histopathological and clinical findings, the final diagnosis was metastatic SCC to the thyroid gland. CLINICAL DISCUSSION: Clinically, patients with thyroid metastasis presented with nonspecific symptoms such as thyroid nodule or goitre, cervical discomfort, dyspnoea, dysphagia, or dysphonia. Chemotherapy is used in the case of a poly metastatic tumour and radiotherapy as a palliative treatment whereas radioiodine treatment is not indicated for thyroid metastases. CONCLUSION: Diagnosis of SCC in the thyroid gland as a primary or metastatic neoplasm is a significant challenge. In the absence of specific clinical or radiological signs, pathological studies remain the gold standard for diagnosis.