CK7/CK20 Double-Negative Pulmonary Enteric Adenocarcinoma With Histopathological Evaluation of Transformation Zone Between Enteric Adenocarcinoma and Conventional Pulmonary Adenocarcinoma:

We report a rare case of pulmonary enteric adenocarcinoma (PEA) exhibiting a immunohistochemical feature of CK7/CK20 double-negativity by evaluating the transformation zone between PEA and conventional pulmonary adenocarcinoma (CPA). A 75-year-old man was found to have a mass, 40 mm in diameter, in the right lower lobe on chest computed tomography, and underwent right lower lobectomy. Histologically, the tumor was composed of a PEA and CPA component. The dominant PEA component had medium to large complex glands with tall columnar cells with eosinophilic cytoplasm and brush-border. The CPA component comprised small to medium glands with cuboidal cells. Moreover, intermediate glands (INT), which had cuboidal to tall columnar cells, with morphological features between PEA and CPA, was also observed in the transformation area. Immunohistochemically, the PEA component was negative for CK7, CK20, and TTF-1, and positive for CDX2 and SATB2 (weak): the CPA component was negative for CK20, CDX2, and SATB2, and pos...