A precursor is an abnormal group of cells that have the potential to turn into cancer over time. Another name for a precursor is a pre-cancerous disease.
Some precursors have a low chance for turning into cancer while others have a very high chance. The chance that a precursor will eventually turn into cancer depends on many factors including:
- The type and location of the precursor disease.
- The size of the precursor disease.
- The grade of the cells in the precursor.
Pathologists look for these changes when examining tissue under the microscope.
What causes a precursor disease?
Precursor diseases can be caused by viruses, genetic changes, or environmental factors. A common virus that causes a precursor disease is human papillomavirus (HPV). Smoking is a common cause for precursor diseases in the mouth, throat, and lungs.
Types of precursor diseases
Doctors often look for precursor diseases so they can be treated before they have a chance to become a cancer. This type of examination is called screening and it is meant to reduce a person’s chance of developing cancer in the future. Common types of screening examinations include the cervical pap test and colonoscopy.
Common types of precursor diseases include:
- High grade squamous intraepithelial lesion (HSIL) – This precursor is caused by a virus called human papillomavirus (HPV). This precursor can cause a cancer called squamous cell carcinoma in the cervix, vulva, vagina, and anal canal.
- Adenomas of the colon – These small growths are very common in adults over 50 years old. Types of adenomas include tubular, villous, and tubulovillous. They are caused by a combination of environmental conditions (for example diet) and genetic changes in the cells that line the inside of the colon. Adenomas can turn into a type of colon cancer called adenocarcinoma. A procedure called a colonoscopy can be performed to look for and remove adenomas in the colon.
- Barretts esophagus – This is a precursor disease that happens in the esophagus. It usually develops after many years of acid reflux disease. Barretts esophagus can turn into a type of esophagus cancer called adenocarcinoma. The chance of developing cancer is low for most people but it increases if your pathologist also sees a change called dysplasia.