The mean age of colorectal cancer in untreated familial adenomatous polyposis (FAP) is 39 years. We present the case of a 21-year-old patient with FAP and colorectal cancer. The patient was detected with significant family history: her mother died at age 45 with colon cancer; two uncles were diagnosed with colon cancer at the age of 40 and 43 and one aunt at the age of 45 with colon cancer and gastric cancer. The treatment was laparoscopic restorative proctocolectomy with total excision of the mesorectum and ileal pouch anal anastomosis completed with endoanal excision of inferior rectal polyps. The histopathological report described a well differentiated rectal adenocarcinoma T1N1aMx developed on a tubulo-villous adenoma located on the rectosigmoid jonction, the rest of the polyps with benign histology.