However, high ABCG4 expression was significantly correlated with lung adenocarcinoma (53.0%) rather than lung squamous cell carcinoma (44.6%) (P<0.001), in poorly (55.2%) rather than well/moderately (42.5%) differentiated NSCLC (P = 0.008), and with increasing tumor node metastasis (TNM) stage II, III and IV (31.0% vs. 53.6% vs. 59.5%, respectively) (P<0.001) (Table 3). Here, ABCG4 is linked to squamous cell lung carcinoma.