Two characteristic features define a cancer: unregulated cell growth and tissue invasion/metastasis. Unregulated cell growth without invasion is a feature of benign neoplasms, or new growths. Cancer is a synonym for malignant neoplasm. Cancers of epithelial tissues are called carcinomas; cancers of nonepithelial (mesenchymal) tissues are called sarcomas. Cancers arising from hematopoietic or lymphoid cells are called leukemias or lymphomas. Cancer is a genetic disease. The malignant phenotype often requires mutations in several different genes that regulate cell proliferation, survival, DNA repair, motility, invasion, and angiogenesis (Table 80-1). Cancer-causing mutations often activate signal transduction pathways leading to aberrant cell proliferation.
