AbstractAim  Patients with germline phosphatase and tensin homologue (PTEN) mutations develop hamartomatous lesions in several organs and are at increased risk of various malignancies. We assessed the lifetime risk of benign and malignant gastrointestinal lesions in patients with a proven PTEN mutation.Method  Data on gender, mutation, dates of birth, last contact, and diagnosis, location and type of gastrointestinal lesions were collected from nine countries. The lifetime risk of gastrointestinal lesions was calculated by Kaplan–Meier methods.Results  A total of 156 patients (67 men, 43%) from 101 families with a PTEN mutation were included. Patients were born between 1928 and 2008. Benign gastrointestinal polyps were reported in 49 (31%) patients at a mean age of 38 years (range 18–62 years) and were most often hamartomas. Twenty‐two (44%) patients had upper as well as lower gastrointestinal lesions, 14 (29%) had only colonic lesions and 13 (27%) had gastrointestinal lesions at unknown sites. The cumulative risk of developing benign gastrointestinal polyps was 70% at age 60. Four patients (two men) developed colorectal carcinoma at 53, 57, 59 and 62 years, respectively. The cumulative risk of developing colorectal carcinoma was 18% at age 60. Except for one carcinoid in the small intestine, no upper gastrointestinal cancers were observed.Conclusion  Benign gastrointestinal lesions are common in PTEN mutation carriers, and a three‐ to four‐fold increased lifetime risk of colorectal cancer compared with the general population may exist. Colorectal screening of patients with germline PTEN mutations is recommended, starting at age 40 years.