Use of caveolin-1, thyroid transcription factor-1, and cytokeratins 7 and 20 in discriminating between primary and secondary pulmonary adenocarcinoma from breast or colonic origin.

The objectives of this study were firstly to compare the immunostaining patterns of antibodies against caveolin-1, thyroid transcription factor-1 (TTF-1), cytokeratin 7 (CK7) and cytokeratin 20 (CK20) in primary and secondary pulmonary adenocarcinomas of breast or colonic origin, and secondly, to investigate their use alone and in combination, in distinguishing between primary and secondary lung adenocarcinomas from breast or colonic origin. Of the 49 lung adenocarcinoma specimens that were enrolled in this study, 30 were primary pulmonary adenocarcinomas, and 19 (9, breast origin; 10, colonic origin) were metastatic pulmonary carcinomas. Immunohistochemical staining was used to detect the expression of caveolin-1, TTF-1, CK7, and CK20. Primary pulmonary adenocarcinoma most often had the CK7-positive/CK20-negative immunohistochemical phenotype and was either TTF-1 positive or caveolin-1 negative. Secondary pulmonary adenocarcinoma of breast origin most often had the CK7-positive/CK20-negative immunohistochemical phenotype and was either TTF-1 negative or caveolin-1 positive, while secondary pulmonary adenocarcinoma of colonic origin most often had the CK20-positive/CK7-negative immunohistochemical phenotype and was either TTF-1 negative or caveolin-1 positive. The results suggest that caveolin-1, TTF-1, or CK7/CK20 alone did not distinguish reliably between primary and secondary pulmonary adenocarcinomas originating from breast or colon. The use of a panel of antibodies that includes TTF-1, caveolin-1, and CK7/CK20 may have higher sensitivity in discriminating between primary adenocarcinomas and metastatic lung adenocarcinomas from breast or colonic origin.