The ErbB4 protein status was not significantly correlated with sex (women, 28.6% vs. men, 54.5%; P = 0.4075), smoking status (never-smokers, 69.4% vs. smokers, 16.9%; P < 0.0001), pathologic subtype (adenocarcinoma, 46.2% vs. nonadenocarcinoma, 51.9%; P > 0.9999), or differentiation status of the lung cancer (well-differentiated, 54.5% vs. others, 48.3%; P > 0.9999).