We analyzed the expression levels and distribution of Prox1 in four thyroid cancer cell lines: TPC1 and BcPAP derived from papillary thyroid carcinoma, and FTC-133 and CGTH-W-1 derived from follicular thyroid carcinoma, as well as in the normal thyroid NTHY cell line, using quantitative real-time reverse transcription-PCR (Q-RT-PCR), Western blot and immunofluorescent analyses. The gene discussed is PROX1; the disease is differentiated thyroid carcinoma.