MUC5AC and oral cavity squamous cell carcinoma: The biological components, pyrimidine, glycoproteins especially mucin, oxygenated hemocyanin, and carotenoids showed differences in the three groups of saliva, normal (n = 21), premalignant (oral leukoplakia, oral submucous fibrosis, (n = 87)), and malignant (oral squamous cell carcinoma, (n = 50)).