The Genetics of Lung Cancer Ninety percent of lung cancers are caused by smoking, but not everyone who smokes will develop lung cancer. Researchers believe that normal genetic variations, known as polymorphisms, may make some people more likely to develop lung cancer if they smoke. The Genetics of Skin Cancer Up to half of all Americans 65 and older will have at least one bout of skin cancer. The most common types of skin cancer in the United States are basal cell and squamous cell carcinomas. These are generally the result of sun exposure. Medullary Thyroid Cancer (MTC) This rare type of thyroid cancer has several forms, depending on the mutations that cause it. Most cases of medullary thyroid cancer, though, are sporadic—they occur without any family history of thyroid cancer. Von Hippel-Lindau Syndrome VHL is a rare genetic disorder marked by an increased risk of developing benign tumors in the brain, spine, retina, and adrenal gland, and cancerous tumors in the kidney.