Expression levels of TYMS, TK-1, and SLC29A1 were all markedly upregulated in HCC compared with normal liver; we confirmed marked upregulation in protein expression of TK-1 in HCC compared with surrounding matched cirrhotic tissue consisting of both regenerative and dysplastic nodules, suggesting that 18F-FLT could be useful in differentiating HCC from surrounding cirrhotic tissue. The gene discussed is TYMS; the disease is hepatocellular carcinoma.