Objective: To evaluate the utility of thyroid transcription factor-1 (TTF-1), surfactant protein-B, (SP-B) cytokeratin 7 (CK7) and CK20 immunostaining in the discrimination between primary adenocarcinomas and metastatic adenocarcinomas.
Methods: Formalin fixed, paraffin embedded tissue blocks from 42 primary lung adenocarcinomas and 30 metastatic carcinomas resected during operation were immunostained with monoclonal antibodies to TTF-1, SP-B, CK7, and CK20.
Results: Positive immunostaining with TTF-1 and SP-B was noted in 74% and 52% of primary lung tumor, respectively. The positive immunostaining and specificity of such a combination for discriminating between primary and metastatic adenocarcinoma were 79% and 94%, respectively. All primary lung adenocarcinomas were CK7 positive, 24 (57%) were CK7 positive/CK20 negative and 18 were CK7 positive/CK20 positive in immunophenotype. Colon and breast were the most common sites of metastasis. All metastatic colorectal adenocarcinomas were CK20 positive, 11 (92%) were CK7 negative/CK20 positive and 1 was CK7 positive/CK20 positive in immunophenotype. The results of cytokeratin immunostaining in the metastatic breast tubular carcinomas were similar to those in the primary lung adenocarcinomas: 4 were CK7 positive/CK20 negative and 4 were CK7 positive/CK20 positive. CK7 positive, and TTF-1 or SP-B positive immunophenotype was seen in 33 (79%) primary lung tumors. A combination of CK7 negative, CK20 positive, and TTF-1 and SP-B negative was highly significantly associated with metastatic colorectal carcinomas compared with either primary lung adenocarcinomas or metastatic breast carcinomas (both P < 0.001). A combination of CK7 positive, CK20 negative, and TTF-1 and SP-B negative was highly significantly associated with metastatic breast carcinomas compared with either primary lung adenocarcinomas or metastatic colorectal carcinomas (both P < 0.001).
Conclusion: Use of a panel of antibodies including TTF-1, SP-B, CK7 and CK20 is helpful in discriminating between primary and metastatic adenocarcinomas of the lung and suggesting the primary sites of some metastatic adenocarcinomas.