SMPD3 and in situ carcinoma: A statistically significant difference in the distribution of β-values was observed between normal vs. dysplasia (one-way ANOVA with Tukey’s multiple comparisons test; F (2, 27) = 9.564, p = 0.007 and q (27) = 4.745, p = 0.007) and normal vs. CIS/OSCC (q (27) = 5.809, p = 0.001), but not dysplasia vs. tumor (q (27) = 1.064, p = 0.735), suggesting that SMPD3 hypermethylation occurs in the dysplasia stage and persists as cells progress towards cancer.