TTF1 and neoplasm: The tumor was diagnosed as invading the visceral pleura and immunohistochemical staining showed caudal-type homeobox transcription factor 2 (CDX-2)(+), mucin-1(+), cytokeratin 7 (CK7)(+) and thyroid transcription factor-1 (TTF-1)(−) in the tumor cells (Fig. 1).