TYMP and neoplasm: The oral fluoropyrimidine capecitabine (Xeloda®; F Hoffmann La-Roche) has been designed to generate 5-FU preferentially in tumours through exploitation of the significantly higher levels of thymidine phosphorylase in tumour tissue compared with healthy tissue (Ishitsuka et al, 1998; Schüller et al, 2000; Miwa et al, 2001).