Primary pulmonary adenocarcinomas with enteric differentiation (PAED) are mainly composed of tall-columnar cells that show similarity to intestinal epithelia and colorectal carcinomas. In this study, we analyzed the immunostaining profiles of 7 PAEDs in comparison with 14 metastatic colorectal carcinomas (MCRs) and 30 usual pulmonary adenocarcinomas (PACs), using antibodies against CDX-2, cytokeratin 7 (CK7), cytokeratin 20 (CK20), TTF-1, surfactant apoprotein-A (SP-A), Napsin A, and MUC2. The positive rates for CDX-2, CK7, CK20, TTF-1, SP-A, Napsin A, and MUC2 were 71%, 100%, 43%, 43%, 14%, 0%, and 43%, respectively, in the PAEDs; 100%, 0%, 86%, 0%, 0%, 0%, and 57% in the MCRs; 3%, 100%, 0%, 93%, 73%, 90%, and 0% in PACs. As expected, immunoreactivity of CDX-2, CK20, and MUC2 was detected in PAEDs. The observed decrease or loss of immunoreactivity for TTF-1, SP-A, and Napsin A indicates that these lesions demonstrate a shift away from their pulmonary phenotype, although CK7 expression was retained. The results indicate that CK7 and CK20 may be useful markers for distinction of PAEDs from MCRs.
From the *Department of Pathology, Cancer Institute, and ‡Department of Chest Surgery, Cancer Institute Hospital, Japanese Foundation for Cancer Research, Tokyo, Japan; †Department of Human and Diagnostic Pathology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan; and §Kanagawa Cancer Center Research Institute, Yokohama, Kanagawa, Japan.
Supported in part by Grants-in-Aid from the Ministry of Education, Culture, Sports, Science and Technology, and by grants from the Ministry of Health, Labour and Welfare, the Smoking Research Foundation, and the Vehicle Racing Commemorative Foundation.
Reprints: Yuichi Ishikawa, MD, PhD, Department of Pathology, JFCR Cancer Institute, 3-10-6 Ariake, Koto-ku, Tokyo 135-8550 Japan (e-mail: firstname.lastname@example.org).