All cancer is genetic, in that it is triggered by altered genes. Genes that control the orderly replication of cells become damaged, allowing the cells to reproduce without restraint.
Cancer usually arises in a single cell. The cell's progress from normal to malignant to metastatic appears to involve a series of distinct changes in the tumor and its immediate environment, and each is influenced by different sets of genes.
![Many Mutations Lead to Cancer](https://webarchive.library.unt.edu/eot2008/20090509124153im_/http://www.cancer.gov/images/Documents/2bb8687b-eb2b-4e62-ba30-a0572dee414e/cancer27.jpg)
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