Most tumors and other neoplastic growths in the body are epithelial in origin.

• The term neoplasia means 'new growth', whereas the term 'tumor' means swelling or enlargement. Most often neoplastic growths come from stratified squamous, simple columnar, or simple cuboidal epithelia.
• While specific reasons for this observation are not known, it clearly relates to the very high rate of cell proliferation that is normal for epithelial tissues.
• For example, the entire epithelial lining of the gastrointestinal tract, from mouth to anus, is completely replaced every five days.
• To the right is an example of a benign colon polyp, representing localized, excessive proliferation of the columnar epithelial lining. The picture was taken during colonoscopy.
   

You need to know the difference between cilia and microvilli.