PLK4 mRNA and protein expression is higher in some anaplastic thyroid carcinoma cell lines compared with the normal thyroid epithelial cells; PLK4 is elevated in papillary thyroid carcinoma patients’ tumor tissues compared with normal thyroid gland tissues; high PLK4 expression is associated with poorer clinicopathologic parameters, correlates with shortened DFS and OS and independently predicts poorer DFS. The gene discussed is PLK4; the disease is thyroid gland undifferentiated (anaplastic) carcinoma.