PDE4A and differentiated thyroid carcinoma: To investigate the impact of the PDE4 family on different subtypes of THCA, we analyzed the mRNA expression levels of PDE4 family in normal tissues (n = 59), classical papillary thyroid carcinoma (PTC) (n = 356), follicular variant of papillary thyroid carcinoma (FVPTC) (n = 104) and columnar cell variant of papillary thyroid carcinoma (CCVPTC) (n = 38) using the TCGA-THCA cohort.