Objective: To describe the diagnosis of a patient with thyroid metastasis from a bronchial carcinoid tumor, initially mistaken for a medullary thyroid carcinoma.Methods: We present the clinical, laboratory, and imaging findings, along with a literature review.Results: Typical bronchial carcinoids are well-differentiated neoplasms, which usually have a good prognosis. However, 15% of the cases may metastasize. This report describes the case of a 36-year-old woman with a history of a surgically removed bronchial carcinoid tumor, which did not relapse after a 4-year follow-up. Nine years later, the patient consulted for a thyroid nodule, and the anatomic pathology report showed a diagnosis of medullary thyroid carcinoma. Subsequently, immunohistochemistry showed that it was a thyroid metastasis from the bronchial carcinoid tumor, which completely changed the treatment and prognosis.
Conclusion:This case highlights the importance of adequate surgery, as well as a detailed review of the past medical history and a proper immunochemistry as part of the histopathologic examination. This will facilitate the distinction between medullary thyroid carcinomas and primary extrathyroid neuroendocrine tumors that have metastasized into the thyroid gland. (AACE Clinical Case Rep. 2018;4:e338-e341) Abbreviations: CT = computed tomography; MRI = magnetic resonance imaging; MTC = medullary thyroid carcinoma; NET = neuroendocrine tumor; PET = positron emission tomography