Invasive carcinoma was detected in only 1/7 (∼14%, proximal colon mucinous adenocarcinoma) Smad3+/− mice necropsied at the experimental endpoint (27 weeks) compared to Smad3−/− mice, where 10/15 animals (∼67%) developed invasive carcinoma (P = 0.0635). Here, SMAD3 is linked to mucinous adenocarcinoma.