SLC22A2 and squamous cell carcinoma: OCT2 rs316019 was significantly associated with squamous carcinoma (additive model: OR 0.42, 95% CI 0.20–0.86, P = 0.018; dominant model: OR 0.42, 95% CI 0.20–0.91, P = 0.028), patients ≤55 years of age (additive model: OR 0.50, 95% CI 0.25–0.97, P = 0.040; dominant model: OR 0.45, 95% CI 0.21–0.94, P = 0.035), being a non-smoker (additive model: OR 0.41, 95% CI 0.20–0.85, P = 0.015; dominant model: OR 0.36, 95% CI 0.17–0.77, P = 0.009), and female patients (dominant model: OR 0.38, 95% CI 0.15–0.95, P = 0.039).