The majority of rectal cancers are adenocarcinomas, which arise from a background of adenomatous dysplasia. The risk factors for developing CRC are numerous. There are adenomatous polyposis syndromes such as familial adenomatous polyposis, hereditary nonpolyposis colorectal cancer, and MUTYH-associated polyposis (MAP) that significantly increase a person's risk of developing CRC. Smoking is also a risk factor. A personal or family history of sporadic CRCs or adenomatous polyps is also concerning. Other inflammatory conditions such as inflammatory bowel disease (especially ulcerative colitis) are risk factors for the development of CRC.
CRC rates are highest among African Americans compared with other populations in the United States. Patients with a low socioeconomic status have also been shown to have an increased risk of developing CRC. The incidence of rectal cancer is higher among men than women. Unlike what has been observed in regard to colon cancers, the incidence of rectal cancer has declined during the last three decades.
Patients with cancers of the rectum or rectosigmoid region often present with hematochezia, tenesmus, and narrowing of the stool. Anemia is uncommon at presentation.
The most common sites of metastasis of colorectal adenocarcinoma are the liver and lungs; rarely, metastatic oral lesions occur.
The US Preventive Services Task Force (USPSTF) recommends screening for CRC using noninvasive blood tests, sigmoidoscopy, or colonoscopy in adults, beginning at age 50 years and continuing until age 75 years. This is due to incidence of CRC increasing significantly around the age of 50 and increasing each decade after that.
C20 – Malignant neoplasm of rectum
254582000 – Adenocarcinoma of rectum
93984006 – Primary malignant neoplasm of rectum