Colorectal adenocarcinoma: risks, prevention and diagnosis

#### What you need to know Colorectal cancer is the fourth most common cause of cancer related mortality globally, with 1.4 million new cases and 700 000 deaths annually.1 Colorectal cancer refers to tumours of the rectum or large bowel (including the appendix) that arise from the colorectal mucosa (fig 1⇓). Adenocarcinoma is the most common form of colorectal cancer (>95%). Rarer subtypes include carcinoid tumour, sarcoma, and lymphoma; these present differently from adenocarcinoma1 and will not be discussed in this review. Fig 1 Distribution of bowel cancer by anatomical site, UK (2007-09) (adapted from Cancer Research UK, bowel cancer incidence statistics, www.cancerresearchuk.org/health-professional/cancer-statistics/statistics-by-cancer-type/bowel-cancer/incidence) Colorectal cancer typically develops from adenomatous polyps that undergo dysplastic changes to become cancerous (fig 2⇓).2 Tumours can occur sporadically, but there are some inherited colorectal cancer syndromes (see table 1⇓). Several risk factors are also recognised (see box 1). Fig 2 Progression from colorectal polyp to cancer (adapted from Johns Hopkins Colon Cancer Center. Polyps 101. www.hopkinscoloncancercenter.org/CMS/CMS\_Page.aspx?CurrentUDV=59&CMS\_Page_ID=744568E4-291E-4276-97C4-FA7A4EE02235) View this table: Table 1 Inherited syndromes predisposing to colorectal cancer #### Box 1: Risk factors for colorectal cancer ##### Sociodemographic factors