View source for Lesion

{{short description|Abnormality in the tissue of an organism}}
{{Infobox medical condition (new)
| name = Lesion
| synonyms = 
| image = 
| caption = 
| pronounce = 
| field = [[Pathology]]
| symptoms = 
| complications = 
| onset = 
| duration = 
| types = 
| causes = 
| risks = 
| diagnosis = 
| differential = 
| prevention = 
| treatment = 
| medication = 
| prognosis = 
| frequency = 
| deaths = 
}}

A '''lesion''' is any damage or abnormal change in the [[tissue (biology)|tissue]] of an [[organism]], usually caused by [[injury]] or [[disease]]s. The term ''Lesion'' is derived from the Latin {{Lang|la|laesio}} meaning "injury".<ref name=":0">{{Cite web |title=Lesion...What Does The Doctor Mean? |url=http://www.medicinenet.com/script/main/art.asp?articlekey=9695 |archive-url=https://web.archive.org/web/20030327094425/http://www.medicinenet.com/script/main/art.asp?articlekey=9695 |url-status=dead |archive-date=March 27, 2003 |access-date=2016-03-03 |website=MedicineNet}}</ref> Lesions may occur in both plants and animals.

== Types ==

There is no designated classification or naming convention for lesions. Because lesions can occur anywhere in the body and their definition is so broad, the varieties of lesions are virtually endless. Generally, lesions may be classified by their patterns, sizes, locations, or causes. They can also be named after the person who discovered them. For example, [[Ghon's complex|Ghon lesions]], which are found in the lungs of those with [[tuberculosis]], are named after the lesion's discoverer, Anton Ghon.<ref name=":0" /> The characteristic [[skin lesion]]s of a [[varicella zoster virus]] infection are called ''[[chickenpox]]''. Lesions of the teeth are usually called [[dental caries]], or "cavities".

=== Location ===

Lesions are often classified by their tissue types or locations. For example, "skin lesions" or "[[brain damage|brain lesion]]" are named for the tissue where they are found. If there is an added significance to regions within the tissue—such as in neural injuries where different locations correspond to different neurological deficits—they are further classified by location. For example, a lesion in the [[central nervous system]] is called a central lesion, and a lesion in the [[peripheral nervous system]] is called a [[Peripheral neuropathy|peripheral lesion]].<ref name=":0" /> A [[Myocardial infarction|myocardial lesion]] results from damage to the heart muscle, and a coronary lesion is a subtype that describes a lesion in the [[Coronary circulation|coronary arteries]]. Coronary lesions are then further classified according to which side of the heart is affected and the diameter of the artery in which they form.<ref>{{Cite journal|last1=Farooq|first1=Vasim|last2=Brugaletta|first2=Salvatore|last3=Serruys|first3=Patrick W.|date=2011-12-01|title=Contemporary and evolving risk scoring algorithms for percutaneous coronary intervention|journal=Heart|volume=97|issue=23|pages=1902–1913|doi=10.1136/heartjnl-2011-300718|issn=1468-201X|pmid=22058284|s2cid=23254704}}</ref>

=== Cause and behavior ===

If a lesion is caused by a [[tumor]], it can be classified as ''[[cancer|malignant]]'' or ''[[benign tumor|benign]]'' after analysis of a [[biopsy]]. A benign lesion that is evolving into a malignant lesion is called "premalignant".<ref name=":0" /> Cancerous lesions are sometimes classified by their growth kinetics, such as the Lodwick classification, which characterizes classes of bone lesions.<ref>{{Cite web|url=http://appliedradiology.com/articles/general-approach-to-lytic-bone-lesions|title=General approach to lytic bone lesions|last1=Bennett|first1=D. Lee|last2=El-Khoury|first2=Georges H.|date=6 May 2004|website=Appliedradiology.com|access-date=2016-03-03}}</ref> Another type is an [[Excitotoxicity|excitotoxic]] lesion, which can be caused by excitatory [[amino acids]] like [[kainic acid]] that kill neurons through overstimulation.

=== Size and shape ===

Lesion size may be specified as ''gross'', meaning it is visible to the unaided eye, or ''[[histologic]]'', meaning a microscope is needed to see it.<ref name="Leeson and Leeson, 1981">{{cite book |last1=Leeson |first1=Thomas S. |last2=Leeson |first2=C. Roland |title=Histology |date=1981 |publisher=W. B. Saunders Company |isbn=978-0-7216-5704-2 |pages=600 |edition= Fourth}}</ref><ref name="Stedman's medical dictionary">{{cite book |title=Stedman's medical dictionary. |year=2006 |publisher=Lippincott Williams & Wilkins |isbn=068340007X |edition=27th |url-access=registration |url=https://archive.org/details/stedmansmedicald00sted_3 }}</ref> A ''space-occupying lesion'', as the name suggests, has a recognizable volume and may impinge on nearby structures, whereas a ''non space-occupying lesion'' is simply a hole in the tissue, such as a small area of the brain that has turned to fluid following a [[stroke]].<ref name=":0" />

Lesions may also be classified by the shape they form, as is the case with many [[Ulcer (dermatology)|ulcers]], which can have a [[Bullseye (target)|bullseye]] or 'target' appearance. A [[coin lesion]] seen in an X-ray has the appearance of a coin sitting on the patient's chest.<ref name=":0" />

== Research using lesions ==

Brain lesions may help researchers understand brain function. Research involving lesions relies on two assumptions: that brain damage can affect different aspects of cognition independently, and that a locally damaged brain functions identically to a normal brain in its "undamaged" parts.<ref name="Kosslyn">{{cite journal | last1=Kosslyn | first1=Stephen M. | last2=Intriligator | first2=James M. | title=Is Cognitive Neuropsychology Plausible? The Perils of Sitting on a Juan-Legged Stool | journal=Journal of Cognitive Neuroscience | volume=4 | issue=1 | year=1992 | pages=96–105 | url=http://nrs.harvard.edu/urn-3:HUL.InstRepos:3595964 | doi=10.1162/jocn.1992.4.1.96 | pmid=23967860 | s2cid=15557071 | url-access=subscription }}</ref>

''Sham lesion'' is the name given to a control procedure during a lesion experiment. In a sham lesion, an animal may be placed in a stereotaxic apparatus and electrodes inserted as in the experimental condition, but no current is passed, so damage to the tissue should be minimal.

=== Research with humans ===

Humans with brain lesions are often subjects of research with the goal of establishing the function of the area where their lesion occurred.<ref>{{Cite journal |last=Adolphs |first=Ralph |date=2016-06-15 |title=Human Lesion Studies in the 21st Century |journal=Neuron |language=en |publisher=Pubmed Central |volume=90 |issue=6 |pages=1151–1153 |doi=10.1016/j.neuron.2016.05.014 |pmc=5656290 |pmid=27311080}}</ref>

A drawback to the use of human subjects is the difficulty in finding subjects who have a lesion to the area the researcher wishes to study. As such, [[transcranial magnetic stimulation]] is often used in cognition and neuroscience-related tests to imitate the effect.<ref>Sliwinska, M. W., Vitello, S., & Devlin, J. T. (2014). Transcranial magnetic stimulation for investigating causal brain-behavioral relationships and their time course. Journal of visualized experiments : JoVE, (89), 51735. {{doi|10.3791/51735}}</ref>

=== Research with animals ===

Using animal subjects gives researchers the ability to study lesions in specific body parts, allowing them to quickly acquire a large group of subjects. An example of such a study is the lesioning of rat hippocampi to establish the role of the [[hippocampus]] in object recognition and object recency.<ref>Albasser, Amin, Lin, Iordanova, Aggelton. Evidence That the Rat Hippocampus Has Contrasting Roles in Object Recognition Memory and Object Recency Memory</ref>

==Notable lesions==
{{columns-list|colwidth=30em|
'''Soft-tissue lesions'''
*[[Morel-Lavallee lesion]]
*[[Bankart lesion]]
*[[Perthes Lesion]]
*[[Stener lesion]]
*[[SLAP lesion]]

'''Diabetes-associated lesions'''
*[[Armanni-Ebstein lesion]]
*[[Blumenthal lesion]]

'''Bone lesions'''
*[[Non-ossifying fibroma]]
*[[ALPSA lesion]]
*[[Hill–Sachs lesion]]
*[[Osteoporosis circumscripta]]
*[[Osteolytic lesion]]

'''Brain lesions'''
*[[Olney's lesions]]

'''Skin lesions'''
*[[Melanocytic nevus]]
*[[Skip lesion]]
*[[Osler's node]]
*[[Keratoderma blennorrhagicum]]
*[[Dermatosis papulosa nigra]]
*[[Leukemid]]
*[[Janeway lesion]]
*[[Kaposi's sarcoma]]
*[[Nevus spilus]]
*[[Chronic scar keratosis]]

'''Gastrointestinal lesions'''
*[[Dieulafoy's lesion]]
*[[Cameron lesions]]

'''Endodermal lesions'''
*[[Melanocytic oral lesion]]
*[[Endometrial intraepithelial neoplasia]]

'''Misc. disease-associated lesions'''
*[[Ghon focus]]
*[[Benign lymphoepithelial lesion]]
*[[Multiple sclerosis lesions]]
*[[Herpes labialis]]
*[[Tropical ulcer]]
*[[Herpetic whitlow]]}}

== See also ==
* [[Ablation]]

==References==
{{reflist}}

== External links ==
{{Sister project links|auto=y}}
{{Medical resources
| ICD10 =
| ICD9 = <!-- {{ICD9|xxx}} --> 
| ICDO = 
| OMIM = 
| DiseasesDB = 
| MedlinePlus = 
| eMedicineSubj = 
| eMedicineTopic = 
| MeshID = 
}}

[[Category:Lesions|Lesions]]
[[Category:Anatomical pathology]]
[[Category:Medical signs]]