A lesion is any abnormal tissue found on or in an organism, usually damaged by disease or trauma. Lesion is derived from the Latin word laesio which means injury.
Lesions are caused by any process that damages tissues. A cancerous tumor is an example of a lesion, however the surrounding tissue damaged by a tumor is also a lesion. Trauma, including electrocution and chemical burns can also cause lesions. Treatment of physical trauma is described here and in First aid. Certain diseases present lesions, for example the skin deformities caused by chicken pox. Lesions can also be caused by metabolic processes, like an ulcer or autoimmune activity, as in the case with many forms of arthritis. Arthritis (from Greek arthro-, joint + -itis, inflammation plural arthritides is a group of conditions involving damage to the Joints of the body
Lesions are sometimes intentionally inflicted during neurosurgery, such as the carefully-placed brain lesion used to treat epilepsy and other brain disorders. Neurosurgery is the surgical discipline focused on treating those central, Peripheral nervous system and spinal column diseases amenable to surgical Epilepsy is a common chronic Neurological disorder that is characterized by recurrent unprovoked seizures.
Note that lesions are not limited to animals or humans; damaged plants are said to have lesions.
Because the definition of lesion is so broad, the varieties of lesions are virtually endless. They are subsequently classified by their features. If a lesion is caused by cancer it will be classified as malignant versus benign. Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled A benign tumor is a Tumor that lacks all three of the Malignant properties of a Cancer. Lesions may be classified by the shape they form, as is the case with many ulcers, which can have a bullseye or 'target' appearance. Ulcers are healing wounds that develop on the skin mucous membranes or eye The bullseye is the center of a target (worth 10 points in Archery or 50 points in Darts) and by extension the name given to any shot that hits the bullseye Their size may be specified as gross or histologic depending on whether they are visible to the unaided eye or require a microscope to see. Histology (from the Greek = 'tissue' is the study of the microscopic anatomy of cells and tissues of Plants and
An additional classification that is sometimes used is based on whether or not a lesion occupies space. A space occupying lesion, as the name suggests, occupies space and may impinge on nearby structures, whereas a non space occupying lesion is simply a hole in the tissue, e. g. a small area of the brain that has turned to fluid following a stroke. A stroke is the rapidly developing loss of brain functions due to a disturbance in the blood vessels supplying blood to the brain
Some lesions have specialized names, like the Gohn lesions in the lungs of tuberculosis victims. The characteristic skin lesions of a varicella-zoster virus (VZV) infection are called chickenpox. Varicella zoster virus ( VZV) is one of eight herpes viruses known to infect humans (and other vertebrates Chickenpox is a highly contagious illness caused by primary infection with Varicella zoster virus (VZV Lesions of the teeth are usually called dental caries. Dental caries is a disease that damages Tooth structures resulting in what is commonly called tooth decay or cavities which are holes in the teeth
Finally, lesions are often classified by their location. For example, compare a 'skin lesion' versus a 'brain lesion'.