A tumor, also known as a neoplasm, is a group of cells that grows beyond normal boundaries. Cells either stop growing or die normally at a given point in time regulated by the cell's controlling mechanism---DNA or RNA. A tumor results when cells multiply out of control.
Definitions
Tumors are said to be benign or malignant in relation to the invasion of surrounding tissues and the ability to spread through the body, reports the National Cancer Institute. Benign tumors only invade local tissues. Malignant tumors invade locally and have the ability to spread through the body.
Cancer
Cancer refers to malignant tumors and not benign tumors, reports Stanford Medicine. Metastasis refers to a malignancy appearing distantly having the same cell type as the original, or primary, tumor from which it spread. According to the National Cancer Institute, a lung tumor, for example, which has metastasized to the brain will have the cell type of the primary lung tumor even though it is found in the brain.
Benign Tumors
Invasion of benign tumors may not be problematic in certain areas such as the skin. Benign tumors of the brain, however, pose problems because of the nature of the brain's activity and because of space issues, according to Stanford Medicine. Diagnostic tests such as X-rays show benign tumors with sharp borders as opposed to malignant tumors defined by unclear invasive borders. Stanford Medicine reports that 75 percent of diagnosed brain tumors are benign.
Tumor Growth
Research at Stanford Medicine's Cancer Center into the paths that lead a normal cell to become cancerous involve oncogenesis, the process by which a gene becomes a cancer gene, and tumor suppression. In DNA mutations, oncogenes lead a cell to become cancerous and uncontrollably multiply. Signaling within the cells plays a major role in tumor spread. Understanding what goes wrong inside a gene, when it is becoming a cancer gene, involves study of the molecules used in nuclear transport, signal processing and the multiplying of genes.
Tumor Suppression
Suppressor genes, studied by another group at Stanford Medicine's Cancer Center, act to suppress tumor growth causing cell death. Stanford reports that the suppressors control cell division in conditions such as DNA damage, a lack of growth factors or defects in the cell. When suppressor genes themselves are mutated, reports the American Society of Clinical Oncologists, cells continue to grow and a tumor may form. Another type of gene, the DNA repair gene, works to fix mistakes when DNA replicates. Mutations are mistakes not repaired in this process. Mutations may lead to the development of cancer, especially if mutations occur in oncogenes or suppressor genes, reports the American Society of Clinical Oncologists.
References
- National Cancer Institute: Malignant versus Benign Tumors
- Stanford Medicine: Benign versus Malignant
- Stanford Medicine: Mechanisms and Pathways of Oncogenesis
- National Cancer Institute: Metastatic Cancer Questions and Answers
- Stanford Medicine: Brain Tumors
- American Society of Clinical Oncology: The Genetics of Cancer
