Skin Lesions

Abscess

An abscess is collection of pus surrounded (walled-off) by damaged and inflamed tissue.
An abscess can occur anywhere on the body. An example of an abscess on the skin is a boil - which is caused by the bacterium staphylococcus aureus.

Cicatrix

The word "cicatrix" is the medical term for what is commonly referred to as a "scar".
That is, it refers to a variety of dermal and epidermal changes associated with wound healing and resulting in fibrous tissue replacing normal tissue in the affected areas.
The adjective associated with "cicatrix" is "cicatricial".

Atrophy (Skin)

Atrophy is the wasting away of normally developed tissue (which may be forming an organ such as the skin) due to cell degeneration. Atrophy of tissue can occur for various reasons, including - for example, ageing, disuse, or undernourishment.

Crust

Crust (in the context of dermatological lesions) refers to an accumulation of
* serum,
* blood, and
* purulent exudate - which is a pus-like liquid that has seeped through the walls of intact blood vessels (usually as a result of inflammation).

Cyst

A cyst is an abnormal sac or closed cavity lined with epithelial tissue cells and filled with liquid liquid, or semi-solid matter. Different types of cyst occur in different parts of the body.

Erosion

In terms of medicine, the term "erosion" refers to the eating away of surface tissue - by chemical or physical processes, such as inflammation. In purely physical terms, "erosion" may also be defined as a loss of epidermis above the basal layer, leaving denuded surface.
Erosion of the skin is a superficial form of ulceration and usually heals quite readily.
(The other medical definition of the term "erosion" is concerned with loss of surface tooth substance - in dentistry.)

Excoriations

Excoriation is the destruction or removal of the surface of the skin (or the tissue covering an organ). This may be caused by scratching, scraping, or chemicals. In cases in which excoriation results from the skin being scratched by the patient due to the irritation of the skin, linear crusts and erosions may result. (This can happen when, for example, the patient has scratched itching eczema or dermatitis while asleep.)

Lesion

Lesions are zones (areas) of tissue whose function is impaired due to damage, usually caused by either disease or wounding. Secondary Lesions such as crusts and scars are derived from Primary Lesions, such as abscesses, ulcers, and tumours.

Lichenification

The term "lichenification" can have two similar meanings in the context of skin lesions.
It can refer to either of:
(1) Thickening of the epidermis of the skin, such that the normal creases appear to be exaggerated. This may be caused by abnormal/excessive scratching or rubbing of the affected area.
(2) Skin that is marked by the presence of many fine papules.

Macule

A macule is a flat circumscribed area of skin of altered skin colour (relative to other skin of the same person). Macules are not elevated above or depressed below the level of surrounding skin, unlike - for example, papules - which are elevated above surrounding skin.

Nodule

A nodule (on the skin) is a small swelling or aggregation of cells foming a palpable lesion of size in range 0.5 cm - 2 cm in diameter. It may be located in the epidermis, dermis, or subcutaneous layers of the skin. In the cases of some skin conditions, many nodules may be present.

Papule

A papule is a small raised spot on the skin that takes the form of a solid palpable lesion of up to
0.5 cm diameter that is elevated above the level of the surrounding skin.

Plaque (Skin)

In the context of the skin (as opposed to its other meaning in dentistry), the term "plaque" refers to a raised lesion whose surface area is much larger than its elevation above the surface of the surrounding skin. This area is usually formed by many papules enlarging or coalescing to form a total area of greater than 2 cm in diameter - though the shape of the area is not necessarily circular, it can take any shape.

Poikiloderma

Poikiloderma is a condition in which skin begins to waste away (atrophy) and becomes pigmented. Poikilodremema is also defined (more technically) as a combination of atrophy, hypo- and hyper-pigmented, and telangiectasis. The result is skin of a mottled discolouration/appearance.

Purpura

Purpura is a type of skin rash that can be considered both as a skin condition, and also as a type of skin leasion. This form of rash results from blood seeping into the skin from small blood vessels called capillaries. The appearance of this rash consists of individual purple spots called petechiae.
Possible causes of purpura include defects in the capillaries and/or deficiency of blood platelets.

Pustule

A pustule is a small blister on the skin that contains pus.
A pustule is a type of abscess , which usually forms in the dermis or subcutis layers of the skin.

Scale

The term "scale" is used to refer to flakes of dead epidermal cells shed by the skin. More specifically, scale consists of the heaping-up of keratin in the stratum corneum of the skin.

Scar

The word "scar" is the common term used to refer to a variety of dermal and epidermal changes associated with wound healing and resulting in fibrous tissue replacing normal tissue in the affected areas. The medical term used to refer to scarring is "cicatrix", or "cicatricial" (adjective).

Sclerosis

Sclerosis is the hardening or "induration" of skin.
Common causes of sclerosis include scarring following inflammation (which is also known as fibrosis), and/or ageing. Note that sclerosis is not just a skin lesion/condition, but can affect different areas of the body - its effects and serious being determined by the area affected and to what extent.

Telangiectasis

A telangiectasis (the singular noun) is a localized group of distended blood capillary vessels.
It appears as a red spot that may look spidery and that blanches when pressure is applied to the telangiectasis directly. (Plural: Telangiectases.)

Ulcer

A (skin) ulcer is a break in the skin such that there is a loss of the epidermis and part or all of the dermis of the skin, leaving a moist depressed lesion. There are many types of skin ulcer, and also ulcers that affect other parts of the body.

Vesicle

A vesicle is a very small blister in the skin that contains a clear liquid called serum.
The sizes of vesicles range from less than 0.1 cm to a maximum of 0.5 cm in diameter.
Vesicles occur in several skin disorders, including eczema and herpes.

Wheal

Wheals are rounded or flat-topped elevated lesions caused by broad flares of swollen skin containing an excessive accumulation of fluid. (The medical term for "swollen with an excessive accumulation of fluid" is "edematous" - though this word is not used in all texts).

A "wheal" or "weal" is also known as a "hive".
These are the common terms for the feature whose medical name is know as "urticaria" (plural). However, "urticaria" are the result of an allergic reaction and the release of histamine. Although this is usually transitory, it can constitute a medical emergency if the lips, eyes, or tongue are affected because considerable swelling can occur.