In the organism

The genetic abnormality responsible for hereditary cancer is in the baby from its first instant of conception. 

This means that, contrary to other types of cancer, the hereditary mutation will be present in every one of the new individual’s cells, throughout his/her life.

The mutation by itself does not cause the disease, but it does increase its chances. 

Tumor suppressor genes

Many of the genes associated with hereditary cancer are involved in protecting the cell from turning cancerous/malignant.

These are distinct genes depending on the cell, but they all act to prevent the disease. For example, by detecting and blocking the growth of an abnormal (malignant) cell until its genetic error is repaired.

When a tumor suppressor gene is changed by a mutation it can become non-functional. In this case malignant cells are no longer “suppressed” and can form tumors.