TYMS and malignant colon neoplasm: We conclude that (1) the p21WAF1+/p53- immunophenotype is associated with a favorable prognosis in patients with stage B2 + C colon cancer treated with 5FU-based chemotherapy, regardless of the level of TS expression, (2) TS expression stratifies patients with colon cancer exhibiting immunophenotypes other than p21WAF1+/p53- and treated with 5FU in two subgroups characterized by a worse (high TS expression) and a better (low TS expression) prognosis.