Papillary adenocarcinoma of lung metastasing to thyroid mimicking papillary thyroid carcinoma

Abstract

Papillary adenocarcinoma of lung is a subtype of lung adenocarcinoma which, based on the new lung adenocarcinoma classification, has aggressive clinical behaviour. Lung adenocarcinoma commonly metastasises to liver, bone and brain. Thyroid is not a common site for metastasis. Here I report a case of papillary adenocarcinoma of lung metastasising to thyroid mimicking primary papillary carcinoma of thyroid clinically and pathologically. The patient was a 72-year-old woman with a history of lung adenocarcinoma who presented with a PET positive nodule in the left lobe of the thyroid. The clinico-pathological dilemma was differentiating a primary papillary carcinoma of thyroid (PTC) which would require completion of thyroidectomy versus a metastatic disease. The histological and immunohistochemical features of this tumour will be discussed as well as a brief review of the literature on this tumour.