Metachronous adenocarcinoma of lung mimicking metastatic papillary thyroid carcinoma: A case report

Introduction: We report an unusual case of adenocarcinoma of lung metachronous with stage IVA papillary thyroid carcinoma. The two tumors are morphologically similar; and the later presence of lung mass could clinically masquerade as metastatic thyroid carcinoma. We discuss the challenges in clinical, imaging and pathologic diagnosis. Case Report: A 64-yearold non-smoking female had a thyroidectomy and neck lymph node dissection for a stage IVA tumor with pathologic findings of one 2 mm microcarcinoma of left thyroid and six positive cervical lymph nodes. The post-surgical I 131 whole body scan was negative and thyroglobulin is suppressed and stable (<1 ng/ml). One year later, she developed a ground glass and part-solid mass in the superior segment of left lower lobe of lung. The mass slowly grew increasing in size from 2.4 cm to 3.3 cm over 3 years. Biopsy of the lung lesion reveals morphologic features of nuclear inclusions and papillae similar to the previously diagnosed thyroid carcinoma. However, the spectrum of atypia, coarse chromatin and lepidic like growth pattern of tumor cells raise suspicion of adenocarcinoma from lung