How to Identify Skin Lesions

A skin lesion on an adult male's leg
A skin lesion on an adult male's leg (Image: intek1/iStock/Getty Images)

A lesion is any abnormality of tissue or organs. To identify a skin lesion, some terms need to be defined so that a standardized vocabulary description can be used. The type of lesion is known as the primary morphology. The configuration (the form or structure) is the secondary morphology. Other words used for describing lesion types include texture, distribution and color. If the eruption is temporary, it is generally a rash. Lesions can range from harmless or common disorders of the skin to serious diseases or illnesses. Any questionable lesion or skin condition should be discussed with a doctor.

Determine the Primary Morphology

Evaluate the symptoms for macules. If the lesion is flat and cannot be felt by touching it, it is generally a macules lesion. These lesions will appear as a color change and be less than 10 mm in diameter. Examples of macules include freckles, measles, allergic reactions to drugs and tattoos. There are times when the lesion can only be seen in a mammogram or ultrasound.

Evaluate the symptoms for papules, plaques or nodules. Papule lesions are elevated and can be felt. A papule is less than 10 mm in diameter. Examples of papules include warts, insect bites, some acne lesions and skin cancers. Plaques are larger palpable lesions. Plaque lesions are greater than 10 mm in diameter. Plaques can be round or flat. An example of a plaque is psoriasis lesions. If the lesion is a firm papule, it can be a nodule. Nodules can extend into the dermis (the tissue between the epidermis and subcutaneous tissue) or into the subcutaneous tissue. Examples of nodules include lipomas, cysts and fibromas.

Evaluate the symptoms for vesicles or bullae. Vesicles look like a blister; they are small and filled with fluid. Vesicles are smaller than 10 mm in diameter. Examples of vesicles are autoimmune disorders that cause blistering and herpes infections. Bullae look like vesicles, but are larger, measuring more that 10 mm in diameter. Bullae can occur when skin is fragile. Examples of Bullae include reactions from bites, burns, drugs and allergic dermatitis.

Evaluate the symptoms for pustules, erosions or ulcers. Pustules are vesicles filled with pus. Pustules can occur because of bacterial infections, inflammatory diseases, folliculitis and pustular psoriasis. Erosions occur when part of the epidermis is missing or open. Erosions can occur due to trauma, scratching, picking, rubbing, infectious diseases or inflammatory diseases of the skin. An ulcer occurs when the epidermis and part of the dermis are destroyed. Ulcers can occur because of trauma, venous stasis dermatitis, infection or vasculitis.

Evaluate the symptoms for urticaria, scales or crusts. Urticarias are hives or wheals. The hives are elevated lesions. Wheals are like hives that last less than 24 hours. Urticaria results from insect bites, stings or drug interactions. Scales are a result of psoriasis, fungal infections and seborrheic dermatitis. The outer layer of skin will be red, thicker and scaly. Crusts are scabs. Scabs consist of dried blood, serum and pus. Crusting can be a result of infections or inflammatory skin diseases.

Evaluate the symptoms for petechiae, purpura or telangiectasis. Petechiae are lesions that have red blood cells outside of the blood vessels. Petechiae are caused by platelet abnormalities, infection, vasculitis and Rocky Mountain spotted fever. Purpuras are like petechiae with a larger hemorrhage area, for example a bruise. Telangiectasis occur with small dilated blood vessels. Telangiectasis is permanent, and can be a result of rosacea, topical use of corticosteroids and systemic diseases.

Determine the Secondary Morphology

Evaluate the shape and arrangement of linear, annular or nummular lesions. Linear lesions will form in a straight line. Examples of linear lesions are contact dermatitis and lichen striatus. Annular lesions will form a ring with the center region appearing to be unaffected. Examples of annular lesions include ringworm, secondary syphilis and some drug reactions. Nummular lesions form a circle. An example of a nummular lesion is nummular eczema.

Evaluate the shape and arrangement of target, serpiginous or reticulated lesions. Target lesions look like a bulls-eye, with rings inside of rings, with a darkened center. An example of a target lesion is erythema multiforme. Serpiginous lesions look like curved branches. Some examples of serpiginous lesions are fungal and parasitic infections. Reticulated lesions have a pattern that resembles lace. Some examples of reticulated lesions are livedo reticularis and cutis marmorata.

Evaluate the shape and arrangement of herpetiform and zosteriform. Groups of papules or vesicles are clustered with no apparent order. Herpetiform and zosteriform are typical reactions to herpes simplex and herpes zoster.

Evaluating the Texture of a Lesion

Determine if the texture of the lession is rough, irregular in shape or has a pebble type appearance. These textures are typical of Verrucous lesions. An example of verrucous lesions is a wart.

Determine if the texture of the skin is thickening and the normal skin marks are accentuated. These characteristics typically result from repeated rubbing of the skin. This type of lesion is called a lichenification. If the thickening is deep, the lesion type is an induration lesion. Induration lesions can be a symptom of cancer, skin infections and skin diseases.

Determine if the lesion is indented in the center. Lesions like this are usually caused from a virus such as herpes simplex.

Determine if the lesion is waxy or yellow. Lesions like this are xanthomas, they usually occur because of a lipid disorder.

Location and Distribution of the Lesion

Locate the lesion. Lesions that are found on the scalp and extensor surfaces (body parts that flex) are likely caused by psoriasis.

Find the lesion. Lesions found on wrists, forearms, lower legs or genitals could be lichen planus lesions.

Locate the lesion. Lesions found on the face may be from vitiligo lesions or chronic cutaneous lupus erythematosus lesions.

Find the lesion. Lesions in warm locations such as the groin or under the breasts could be from hidradenitis.

The Color of the Lesion or Skin

Determine color. Red or pink skin or lesions are typically caused by inflammatory or infectious diseases.

Determine color. Violet or purple skin or lesions are typically caused by vasculitis or cutaneous hemorrhages.

Determine color. Black skin or lesions are typically caused by dead skin due to infection, arterial insufficiency or vasculitis.

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