title: Genetic testing for young-onset colorectal cancer: case report and evidence-based clinical guidelines.
abstract: BACKGROUND
  Young-onset colorectal cancer is clinicopathologically different from older-onset colorectal cancer and tends to occur in patients with hereditary germline conditions such as Lynch syndrome and familial adenomatous polyposis.
  
  
  METHODS
  We describe the case of a 44-year-old man with a paternal history of colon polyps, a personal 2-year history of hematochezia, and a diagnosis of rectal cancer. Further clinical evaluation of the patient at our institution determined the cancer to be stage IIIA. The patient underwent genetic counseling and testing, which indicated he was negative for the most common familial cancer syndromes. After treatment with neoadjuvant chemoradiotherapy, surgery, and adjuvant chemotherapy, the patient has done well. We review the hereditary cancer syndromes and genetic tests to consider for patients with early-onset colorectal cancer.
  
  
  CONCLUSIONS
  This case underscores the importance of following cancer-screening guidelines.
authors.affiliation: Mayo Medical School, College of Medicine, Mayo Clinic, Rochester, Minnesota.
authors.forename: Yaolin
authors.initials: Y
authors.lastname: Zhou
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Boardman
authors.forename: Robert C
authors.initials: RC
authors.lastname: Miller