Definition of Lesion
Lesion definition - medical term Pronounced "lee-sion" with the emphasis on the "lee," a lesion
can be almost any abnormality involving any tissue or organ due to any disease or
There are, not surprisingly, many types of lesions. There are also a number of
different ways of classifying and naming lesions. Lesions can, for instance, be
categorized according to whether or not they are caused by cancer. A benign lesion
is non-cancerous whereas a malignant lesion is cancerous. For example, a biopsy
of a skin lesion may prove it to be benign or malignant, or evolving into a malignant
lesion (called a premalignant lesion).
Lesions can be defined according to the patterns they form. For example, a bull's-eye
or target lesion is one that looks like the bull's eye on a target. (In an X-ray
of the duodenum, a bull's-eye lesion can represent a tumor with an ulcer (crater)
in the center.) A coin lesion is a round shadow resembling a coin on a chest X-ray.
It, too, is usually due to a tumor.
Lesions can be named for persons who first described them. For instance, a Ghon
lesion (or Ghon focus) is the scar-like "signature" in the lungs of adults left
by tuberculosis in childhood.
Lesions can also be categorized by their size. A gross lesion is one that can
be seen with the naked eye. A microscopic or histologic lesion requires the magnification
of a microscope to be seen. The basis of sickle cell disease is a molecular lesion,
one that is not even visible with a microscope but is only detectable on the molecular
(protein or DNA) level.
Location is another basis for naming lesions. In neurology, a central lesion
involves the brain or spinal cord, i.e., the central nervous system. A peripheral
lesion involves the nerves away from the spinal cord and does not involve the central
There is a virtually endless assortment of lesions in medicine: primary lesions,
secondary lesions, impaction lesions, indiscriminate lesions, irritative lesions,
etc. Many are named for people including the Armanni-Ebstein lesion, a Bankart lesion,
a Blumenthal lesion, and so on.
The word "lesion" comes from the Latin noun "laesio" meaning "an attack or injury"
which is related in Latin to the verb "laedere" = "to hurt, strike or wound."