Seborrheic keratosis

Definition

A skin lesion is a superficial growth or patch of the skin that does not resemble the area surrounding it.

Description

Skin lesions can be grouped into two categories: primary and secondary. Primary skin lesions are variations in color or texture that may be present at birth, such as moles or birthmarks, or that may be acquired during a person's lifetime, such as those associated with infectious diseases (e.g. warts, acne, or psoriasis), allergic reactions (e.g. hives or contact dermatitis), or environmental agents (e.g. sunburn, pressure, or temperature extremes). Secondary skin lesions are those changes in the skin that result from primary skin lesions, either as a natural progression or as a result of a person manipulating (e.g. scratching or picking at) a primary lesion.

The major types of primary lesions are:

• Macule. A small, circular, flat spot less than ²/₅ in (1 cm) in diameter. The color of a macule is not the same as that of nearby skin. Macules come in a variety of shapes and are usually brown, white, or red. Examples of macules include freckles and flat moles. A macule more than ²/₅ in (1 cm) in diameter is called a patch.
• Vesicle. A raised lesion less than ¹/₅ in (5 mm) across and filled with a clear fluid. Vesicles that are more than ¹/₅ in (5 mm) across are called bullae or blisters. These lesions may may be the result of sunburns, insect bites, chemical irritation, or certain viral infections, such as herpes.
• Pustule. A raised lesion filled with pus. A pustule is usually the result of an infection, such as acne, imptigeo, or boils.
• Papule. A solid, raised lesion less than ²/₅ in (1 cm) across. A patch of closely grouped papules more than ²/₅ in (1 cm) across is called a plaque. Papules and plaques can be rough in texture and red, pink, or brown in color. Papules are associated with such conditions as warts, syphilis, psoriasis, seborrheic and actinic keratoses, lichen planus, and skin cancer.
• Nodule. A solid lesion that has distinct edges and that is usually more deeply rooted than a papule. Doctors often describe a nodule as "palpable," meaning that, when examined by touch, it can be felt as a hard mass distinct from the tissue surrounding it. A nodule more than 2 cm in diameter is called a tumor. Nodules are associated with, among other conditions, keratinous cysts, lipomas, fibromas, and some types of lymphomas.
• Wheal. A skin elevation caused by swelling that can be itchy and usually disappears soon after erupting. Wheals are generally associated with an allergic reaction, such as to a drug or an insect bite.
• Telangiectasia. Small, dilated blood vessels that appear close to the surface of the skin. Telangiectasia is often a symptom of such diseases as rosacea or scleroderma.

The major types of secondary skin lesions are:

• Ulcer. Lesion that involves loss of the upper portion of the skin (epidermis) and part of the lower portion (dermis). Ulcers can result from acute conditions such as bacterial infection or trauma, or from more chronic conditions, such as scleroderma or disorders involving peripheral veins and arteries. An ulcer that appears as a deep crack that extends to the dermis is called a fissure.
• Scale. A dry, horny build-up of dead skin cells that often flakes off the surface of the skin. Diseases that promote scale include fungal infections, psoriasis, and seborrheic dermatitis.
• Crust. A dried collection of blood, serum, or pus. Also called a scab, a crust is often part of the normal healing process of many infectious lesions.
• Erosion. Lesion that involves loss of the epidermis.
• Excoriation. A hollow, crusted area caused by scratching or picking at a primary lesion.
• Scar. Discolored, fibrous tissue that permanently replaces normal skin after destruction of the dermis. A very thick and raised scar is called a keloid.
• Lichenification. Rough, thick epidermis with exaggerated skin lines. This is often a characteristic of scratch dermatitis and atopic dermatitis.
• Atrophy. An area of skin that has become very thin and wrinkled. Normally seen in older individuals and people who are using very strong topical corticosteroid medication.

Causes and symptoms

Skin lesions can be caused by a wide variety of conditions and diseases. A tendency toward developing moles, freckles, or birthmarks may be inherited. Infection of the skin itself by bacteria, viruses, fungi, or parasites is the most common cause of skin lesions. Acne, athlete's foot (tinea pedis), warts, and scabies are examples of skin infections that cause lesions. Allergic reactions and sensitivity to outside environmental factors can also lead to the formation of skin lesions. Underlying conditions can also precipitate the appearance of skin lesions. For example, the decreased sensitivity and poor circulation that accompanies diabetes mellitus can contribute to the formation of extensive ulcers on extremities such as the feet. Infections of body's entire system can cause the sudden onset of skin lesions. For example, skin lesions are a hallmark symptom of such diseases as chicken pox, herpes, and small pox. Cancers affecting the skin, including basal cell carcinoma, squamous cell carcinoma, malignant melanoma, and Kaposi's sarcoma, are recognized by their lesions.

Diagnosis

Diagnosis of the underlying cause of skin lesions is usually based on patient history, characteristics of the lesion, and where and how it appears on the patient's body (e.g. pustules confined to the face, neck and upper back can indicate acne, while scales appearing on the scalp and face may indicate seborrheic dermatitis). To determine the cause of an infection, doctors may also take scrapings or swab samples from lesions for examination under a microscope or for use in bacterial, fungal, or viral cultures. In cases where a fungal infection is suspected, a doctor may examine a patient's skin under ultraviolet light using a filter device called a Woods light--under these conditions, certain species will taken on specific fluorescent colors. Dermatologists may also use contrast lighting and subdued lighting to detect variations in the skin. When involvement of the immune system is suspected, doctors may order a immunofluorescence test, which detects antibodies to specific antigens using a fluorescent chemical. In cases of contact dermatitis, a condition in which a allergic reaction to something irritates the skin, doctors may use patch tests, in which samples of specific antigens are introduced into the skin via a scratch or a needle prick, to determine what substances are provoking the reaction.

The vast majority of skin lesions are noncancerous. However, doctors will determine whether or not a particular lesion or lesions are cancerous based on observation and the results of an excisional or punch biopsy, in which a tissue sample is excised for microscopic analysis. Since early detection is a key to successful treatment, individuals should examine their skin on a monthly basis for changes to existing moles, the presence of new moles, or a change in a certain area of skin. When examining moles, factors to look for include:

• Asymmetry. A normal mole is round, whereas a suspicious mole is uneven.
• Border. A normal mole has a clear-cut border with the surrounding skin, whereas the edges of a suspect mole may be irregular.
• Color. Normal moles are uniformly tan or brown, but cancerous moles may appear as mixtures of red, white, blue, brown, purple, or black.
• Diameter. Normal moles are usually less than ¹/₅ in (5 mm) in diameter, a skin lesion greater than this may be suspected as cancerous.

Treatment

Treatment of skin lesions depends upon the underlying cause, what type of lesions they are, and the patient's overall health. If the cause of the lesions is an allergic reaction, removing the allergen from the patient's environment is the most effective treatment. Topical preparations can also be used to clean and protect irritated skin as well as to remove dead skin cells and scales. These may come in a variety of forms, including ointments, creams, lotions, and solutions. Topical antibiotics, fungicides, pediculicides (agents that kill lice), and scabicides (agents that kill the scabies parasite) can be applied to treat appropriate skin infections. Oral medications may be taken to address systemic infections or conditions. Deeply infected lesions may require minor surgery to lance and drain pus. Topical agents to sooth irritated skin and reduce inflammation may also be applied. Corticosteroids are particularly effective in reducing inflammation and itching (puritis). Oatmeal baths, baking soda mixtures, and calamine lotion are also recommended for the relief of these symptoms. A type of corticosteroid may be used to reduce the appearance of keloid scars. Absorbent powders may also be used to reduce moisture and prevent the spread of infection. In cases of ulcers that are slow to heal, pressure dressings may be used. At times, surgical removal of a lesion may be recommended--this is the usual course of therapy for skin cancer. Surgical removal usually involves a simple excision under local anesthetic, but it may also be accomplished through freezing (cryotherapy) or laser surgery.

Prognosis

Skin lesions such as moles, freckles, and birthmarks are a normal part of skin and will not disappear unless deliberately removed by a surgical procedure. Lesions due to an allergic reaction often subside soon after the offending agent is removed. Healing of lesions due to infections or disorders depends upon the type of infection or disorder and the overall health of the individual. Prognosis for skin cancer primarily depends upon whether or not the lesion is localized and whether or not it has spread to other areas of the body, such as the lymph nodes. In cases where the lesion is localized and has not spread to other parts of the body, the cure rate is 95-100%.

Prevention

Not all skin lesions are preventable; moles and freckles, for example, are benign growths that are common and unavoidable. However others can be avoided or minimized by taking certain precautions. Skin lesions caused by an allergic reaction can be avoided by determining what the offending agent is and removing it from the home or workplace, or, if this is impossible, developing strategies for safely handling it, such as with gloves and protective clothing. Keeping the skin, nails, and scalp clean and moisturized can help reduce or prevent the incidence of infectious skin diseases, as can not sharing personal care items such as combs and make-up with others. Skin lesions associated with sexually transmitted diseases can be prevented by the use of condoms. Scratching or picking at existing lesions should be avoided since this usually serves only to spread infection and may result in scarring. Individuals who have systemic conditions, such as diabetes mellitus or poor circulation, that could lead to serious skin lesions should inspect their bodies regularly for changes in their skin's condition. Regular visual inspection of the skin is also a key to preventing or minimizing the occurrence of skin cancer, as is the regular use of sun screens with an SPF of 15 or more.

Key Terms

Corticosteroid

A type of steroid medication that helps relieve itching (puritis) and reduce inflammation.

Fibroma

A usually benign tumor consisting of fiborous tissue.

Lesion

A possibly abnormal change or difference in a tissue or structure, such as the skin.

Lipoma

A usually benign tumor of fatty tissue.

Patch test

Test in which different antigens (substances that cause an allergic reaction) are introduced into a patient's skin via a needle prick or scratch and then observed for evidence of an allergic reaction to one or more of them. Also known as a scratch test.

Woods light

Device that allows only ultraviolet light to pass through it.

Further Reading

For Your Information

Books

• Leibrandt, Thomas, ed. Nurse's Reference Library: Diseases. Springhouse, PA: Springhouse Corporation, 1985.
• Rosen, Theodore, Marilyn B. Lanning, and Marcia J. Hill. The Nurse's Atlas of Dermatology. Boston: Little Brown & Company, 1983.
• Turkington, Carol. Skin Deep: An A-Z of Skin Disorders, Treatments and Health. New York: Facts on File, Inc. 1996.

  Other

• Keloids. http://www.skinsite.com/info_keloids.htm (7 April 1998).
• Seborrheic Keratoses. http://www.aad.org/aadpamphrework/saborr kera.html (7 April 1998).
• Skin lesions. http://www.medicine.dal.ca/smed/sgb/dermsite/lesions.html (7 April 1998).
• Skin lesions, benign. http://www.thriveonline.com/health/Library/illsymp/illness482.html (6 April 1998).

Gale Encyclopedia of Medicine. Gale Research, 1999.