Why are people born with cancer?

Why are people born with cancer ?
Actually this is a difficult question to answer. Rather than people who are born with a cancer I would like to talk about the cancers which develop in first few years of life. As you might already know any cell in the body can become malignant. There are specific cell lines in the body which are existent only in the first few years of the life and are not found in the adults. Hereditary retinoblastoma is an example of this. More genetic mutations the zygote has there is a greater chance of developing a cancer in the early life.
Certain malignancies can develop in the intra uterine life and can ultimately lead to spontaneous abortions. Actually most of the genetic mutations lead to spontaneous abortions.