Thyroid transcription factor-1, cytokeratin 7 and cytokeratin 8 for differentiating primary and metastatic lung adenocarcinoma

Adenocarcinomas are the most common cause of malignancy in pleura fluids. Usual primary sites include the lung, breast, gastrointestinal tract and genitourinary tracts. Predicting the site of origin of an adenocarcinoma is difficult due to overlapping morphologic characteristics. Thyroid transcription factor-1 (TTF-1), Cytokeratin7 (CK7) and Cytokeratin8 (CK8) were investigated to differentiate the primary and metastatic lung adenocarcinoma in 14 pleura fluid samples. There was a significant difference between TTF-1, CK 7 and CK 8 expressions in primary lung adenocarcinomas (P=0.028; Chi-squared test) and in metastatic lung adenocarcinomas (P=0.004; Chi-squared test). The sensitivity of TTF-1, CK7 and CK8 as a marker for primary lung adenocarcinomas were 0, 87 and 57%, respectively. Moreover, the sensitivity of TTF-1, CK7 and CK8 as a marker for metastatic lung adenocarcinomas were 16, 86 and 75%, respectively. Overall results for primary lung adenocarcinomas demonstrated CK8 reactivity in 4 (57%) of 7 cases. Nine metastatic lung adenocarcinoma samples (75%) were positive for CK8. TTF-1 was expressed in 16% of metastatic lung adenocarcinomas, but negative TTF-1 staining was observed in all primary lung adenocarcinoma cases. It was concluded that these results confirmed that the method of TTF-1, CK7 and CK8 immunohistochemistry is not sensitive enough for the differential diagnosis of primary and metastatic lung adenocarcinomas. © IDOSI Publications, 2010