Adenocarcinoma of the Colon and Rectum

Colorectal cancer comes in many forms, including adenocarcinoma, leiomyosarcoma, lymphoma, melanoma, and neuroendocrine tumors. This article discusses adenocarcinomas, which account for about 90-95 percent of all colorectal cancers.

Definition of Adenocarcinoma

Let's break it down. "Adeno-" is a prefix that means "gland." In general, glands secrete things and are classified as endocrine or exocrine. Endocrine glands secrete things into the bloodstream, like hormones. Exocrine glands secrete things that go outside of the body, like mucus and sweat.

A carcinoma is a malignant tumor that starts in epithelial tissue. Put the two words together and you get "adenocarcinoma," which means a malignant tumor in epithelial tissue, specifically in a gland.

Cause of Adenocarcinoma

Virtually all adenocarcinomas develop from adenomas. In general, the bigger the adenoma, the more likely it is to become cancerous. For example, polyps larger than two centimeters (about the diameter of a nickel) have a 30-50 percent chance of being cancerous. You can learn more about polyp size and colon cancer risk by viewing the Polyp Size Gallery.

By the time colorectal cancer is diagnosed, it has often been growing for several years, first as a non-cancerous polyp (adenoma) and later as cancer. Research indicates that by age 50, one in four people has polyps.

Subtypes of Adenocarcinoma

Two subtypes of adenocarcinoma include signet ring cell adenocarcinoma and mucinous adenocarcinoma. Signet ring cell adenocarcinoma is named for the way its cells look under a microscope. Mucinous adenocarcinoma is referred to as "mucinous" because its cells contain so much mucus.

• Aggressive Neuroendocrine Tumor
  
• Leiomyosarcoma
  
• Lymphoma
  
• Malignant Melanoma
  
• Mucinous Adenocarcinoma
  
• Signet Ring Cell Adenocarcinoma