What is Alpha feto protein?

I checked it out in the internet and read that it is mostly found in high degrees in infants. My sister had recently taken a blood test that includes cancer markers. The result was positive for AFP. She is 18 now.

What could be the reason for higher levels of AFP? It was said to be a symptom of liver or ovarian cancer. But are there other reasons or explanations to this thing called AFP present in the body?

Alpha-fetoprotein (AFP) is a molecule produced in the developing embryo and fetus. In humans, AFP levels decrease gradually after birth, reaching adult levels by 8 to 12 months. Normal adult AFP levels are low, but detectable; however, AFP has no known function in normal adults.

There are other reasons for it to be present, such as pregnancy, some tumors, hodgkins disease, lymphoma and kidney cancer, as well as cirrhosis of the liver, and chronic active hepatitis.