Definition
What is a tumor?
A tumor, also called a neoplasm (literally, new growth), is a lump of tissue that forms when the normal balance between cell division and cell death is lost. Cells keep multiplying when the body has no need for them, or old and damaged cells survive when they should be cleared away, so the mass keeps enlarging. Not every swelling is a tumor: a lump caused by infection or trapped fluid is not a neoplasm.
Tumors fall into two broad groups. Benign tumors stay where they started and do not invade, so surgery can often remove them completely. Malignant tumors are cancers: they grow into neighboring tissue and can shed cells that travel through blood or lymph to form secondary tumors elsewhere. Some cancers, such as most leukemias, do not form solid tumors at all.
Most tumor names end in -oma and name the tissue of origin. A lipoma is a benign tumor of fat, while carcinomas and sarcomas are malignant tumors of epithelium and connective tissue. A pathologist decides what kind a tumor is by examining a biopsy under the microscope.
Word parts
Where does the word “tumor” come from?
- tumor
- a swellingLatin tumor, from tumere, to swell
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Terms that go with it
- Benign tumorA benign tumor is an abnormal growth of cells that stays in one place and does not invade nearby tissue or seed new growths elsewhere.
- Malignant tumorA malignant tumor is a cancerous mass whose cells grow without control, invade surrounding tissue and can spread to distant organs.
- CancerCancer is a group of diseases in which abnormal cells divide without control, invade nearby tissue and can spread to distant parts of the body.
- MetastasisMetastasis is the spread of a cancer from its first site to distant organs, where escaped cells settle and grow into secondary tumors.
- CarcinomaA carcinoma is a cancer that starts in epithelial cells, the cells that cover the skin and line the inner and outer surfaces of organs.
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Written for biofideX in plain words, after checking these references:
- NCI Dictionary of Cancer Terms: tumor
- OpenStax Biology 2e, 10.4 Cancer and the Cell Cycle
- MedlinePlus: Benign Tumors
- Cancer Research UK: Types of cancer
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