Types of Skin Lesions

When an area of soft tissue in the body, is damaged or destroyed, a lesion is the sign of the damage. Any body area with vulnerable tissue can have lesions, but one of the most sensitive areas is the skin. Lesions on the skin can be formed by external causes or internal conditions. Some lesions are harmless and are just indicators of injury or the healing process. But some types of skin lesions can cause or be a cause of skin diseases and even cancer.

Skin Lesions Types

There are 2 main categories of skin lesions: primary and secondary.

Types of Skin Lesions - Primary
Primary skin lesions are formed due to a disease or infection. They can cause a change in skin color or texture. Moles and freckles can be considered as primary lesions, which are formed at birth and not due to a disease. Primary skin lesions are often categorized as a morphological classification of skin lesions, as this classification deals with the physical features and location of the lesions. A tabular representation of various primary skin lesions types, with their size, characteristics and causes, is shown below.

Name/Feature	Size	Color	Description	Caused By
Macule	Less than 10 mm	Brown, white, red	Flat, discolored	Hives, leprosy, measles, rashes
Nodule	0.5 - 2 cms	None	Distinct borders, hard and deep into the skin	Inflammation, tuberculosis, roundworms
Pustule	Varies	White, yellow, greenish-yellow	Pus filled, elevated	Bacterial infections
Papule	Less than 10 mm	Red, pink, brown	Raised, rough, solid	Warts, syphilis, psoriasis
Plaque	Less than 10 mm	Same as Papule	Solid, elevated, flat or circular topped	Psoriasis
Bulla	Greater than 1 cm	Clear	Fluid filled	Burns, bites, drug reactions
Wheal	3 - 4 mm	Pale red	Raised, rounded, flat topped	Allergic reactions
Vesicle	Less than 1 cm	Clear	Filled with fluid, elevated	Herpes, allergies, sunburn
Tumor	Greater than 2 cm	None	A large nodule	No certain causes
Telangiectasia	None	None	Dilated blood vessels close to skin's surface	Rosacea, scleroderma

Types of Skin Lesions - Secondary
If the disease or infection worsens, then primary lesions progress to secondary lesions. Some secondary lesions are caused by insistent physical contact with the infected area, like if the infected skin is repeatedly itched or nicked.

1. Scale
   • Dry or greasy in texture
   • Present on the skin in a flaky or scale-like form
   • Caused by fungal infections and psoriasis
2. Crust (Scab)
   • Serum, pus or blood which has dried and pooled on the skin
   • Can be thick and sticking to the skin or thin and easily torn
   • Part of the healing process
3. Keloids
   • Exaggerated or swollen scar tissue, that extends beyond the edges of the original wound
   • Tough and rubbery in texture, with a shiny appearance
   • Can be flesh-colored, pink or dark red in color
   • Formed from a mature scar
4. Lichenification
   • Thickening of the skin, so that the area becomes elevated
   • Visible marks appear
   • Caused by rubbing or deep scratching of an area
5. Erosion
   • Small areas of the skin, in which the upper skin layer is lost
   • Caused by various infectious skin diseases like herpes
6. Fissure
   • A narrow, deep crack on the skin, extending to the flesh
   • Caused due to excessive drying of the skin
   • Occurs at corners of the mouth and on hands and feet
7. Atrophy
   • A very wrinkled and thin area of the skin
   • Example of atrophied skin is stretch marks
   • Caused due to old age, prolonged sun exposure, strong corticosteroids creams
8. Ulcers
   • A discontinuous loss of the skin, sometimes reaching the fat layer
   • The upper portion and part of the lower portion, of the skin, is lost
   • Caused by bacterial infections or injury
9. Scars
   • Discolored tissue, that permanently replaces the skin in that area
   • Scars differ in color, depending on the skin area
   • Some scars are thick and raised, others depressed

Lesions can also be classified under their configuration style. Linear lesions are a cluster of lesions in a straight line. Annular and Nummular are ringed and circular-shaped lesion configurations. Iris lesions have rings, with a duskier or darker center group of lesions. Lesions are also a known indicator of skin cancer. Precancerous skin lesions are lesions, which could progress into cancer, if not identified in time. The most common of all the types of precancerous skin lesions, is Actinic Keratosis. It is made up of red, scaly lesions, occurring on the face, ears and the back of the hands. If no treatment is given, then a small portion of these lesions may develop into squamous cell carcinoma, a skin cancer. Cutaneous horns are also precancerous. They appear as a small horn or conical lump that extend from a red skin base. These are common among elderly fair people, with a history of sun exposure. Dysplastic Nevus or Moles are cancerous, when the mole has multiple colors or uneven borders or is abnormally large.

Since there are different types of lesions on the skin, the treatment depends on the cause. Skin lesions caused by infections, are cured by treatment of the infection itself. Allergy lesions are best solved by avoiding the allergen. Skin preparations like creams, lotions and ointments can help in preventing infection and soothing the lesion. In some cases such as pus-filled lesions or skin cancer, a minor surgical operation might have to be performed.