Diagnostic utility of PAX8, TTF-1 and napsin A for discriminating metastatic carcinoma from primary adenocarcinoma of the lung.

The differential expression of PAX8 and TTF-1 may prove useful in distinguishing between neuroendocrine carcinomas of pulmonary and thymic origin

useful in distinguishing thymic carcinoma from poorly differentiated lung carcinoma

Data shows that PAX8 provides signals for growth and motility of non-small cell lung cancer cells and is necessary for MET and RON expression.

PAX8 was negative in all cases of pulmonary neuroendocrine carcinoma (PNEC) while positive in 86.4% of thymic cases (TNEC). TTF-1 positivity was associated with high sensitivity but low specificity for PNEC, and adding PAX8 negativity significantly increased the specificity. PAX8 positivity alone showed essentially 100% specificity and 86.4% sensitivity for TNEC.

this study shows that PAX-8 positivity is rare in primary lung carcinoma