A mimic of lung adenocarcinoma: a case report of histological conversion of metastatic thyroid papillary carcinoma.

This finding suggests a collision of metastatic thyroid papillary carcinoma and lung adenocarcinoma, because the morphological features were different between the adenocarcinoma-like tumour (C, lower half) and the metastatic papillary carcinoma (C, upper half). A pleural nodule was found to be adhering to the surface of the resected lower lobe specimen; the nodule was composed of adenocarcinoma, so pleural dissemination of lung adenocarcinoma was suspected. The marked small nodule adjacent to the primary tumour was a small metastasis of papillary thyroid carcinoma, and similar nodules were scattered in the outside lung parenchyma. [Extracted from the article]