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Some cancers occur in people with no family history and no specific inherited gene variant known to increase risk:
- This type of cancer is called sporadic.
- In sporadic cancer, the gene variants are in the tumor only rather than in the other healthy cells.
- This type of sporadic cancer usually is caused by nongenetic factors, such as aging, exposure to carcinogens and lifestyle choices.
- The majority of breast cancers are sporadic.