Cancer begins when a cell begins dividing uncontrollably. Eventually these cells form a visible mass or tumor. Solid tumors are masses of abnormal tissue that originate in organs or soft tissues that typically do not include fluid areas and cysts. Solid tumors are typically named after the types of cells that compose them. Some examples of solid tumors include: breast cancer, prostate cancer, lung cancer, liver cancer, pancreatic cancer, and melanoma. Cancer cells divide into twins. One of the twins will actually begin to form tissues while the other twin does nothing, it lies dormant. What prevents it from growing further is the immune system. As we get older, or if we’re under a great deal of stress, our immune system weakens and the cancers can grow.