Table 2 showed the probability of SCLC: the higher the levels of ProGRP and/or NSE, the greater the probability of SCLC. The combination of NSE and ProGRP increased sensitivity and specificity in diagnosing SCLC. SCC was better than the other tumor markers in the discrimination between squamous carcinoma and adenocarcinoma. The AUC of SCC was greater than that for the remaining markers (Figure 1). These tumor markers were not useful in discriminating adenocarcinoma and large cell carcinoma. We classified large cell carcinoma as adenocarcinoma in the present study (Figure 1). This evidence concerns the gene ENO2 and large cell carcinoma.