MORPHOLOGY - The form or structure of an individual skin lesion.
LESION - Any single area of altered skin. Lesions may be solitary or multiple.
PRIMARY LESION - A lesion directly associated with the disease process that is described with established dermatological terminology.
Example: Macule, papule, patch, plaque, vesicle, bulla, and others
SECONDARY LESION - Modification of a primary lesion that results from evolution of the primary lesion, traumatic injury, or other external factors.
Example: Erosion, fissure, ulceration, excoriation, and others
MACULE - A circumscribed, flat area of discoloration that is less than 10 mm* in diameter.
PATCH - A circumscribed, flat area of discoloration that is greater than 10 mm* in diameter. Slight scale may or may not be present.
PAPULE - A circumscribed, elevated, solid lesion that is less than 10 mm* in diameter.
PLAQUE - A circumscribed, elevated, solid lesion that is greater than 10 mm* in diameter and is usually broader than it is thick.
NODULE - A palpable, solid lesion that is greater than 10 mm* in diameter. Nodules are usually found in the dermal or subcutaneous tissue, and the lesion may be above, level with, or below the skin surface.
TUMOR - A solid, firm lesion that is typically greater than 20 mm in diameter. Tumors can be above, level with, or beneath the skin surface. Also known as a mass.
Example: Metastatic carcinoma
WEAL - Transient, circumscribed, edematous papules or plaques caused by swelling in the dermis. Wheals may manifest with erythematous borders and pale centers and/or a narrow peripheral zone of pallor or vasoconstriction.
BURROW - A thread-like linear or serpiginous (wavy, serpent-like) tunnel in the epidermis typically made by a parasite.
EROSION - A shallow, moist, or crusted lesion resulting from the loss of the superficial layers of the upper epidermis only, as from friction or pressure.
Example: Ruptured varicella vesicles
EXCORIATION - A skin abrasion that is usually superficial and due to scratching of the skin. Excoriations may be linear or focal.
Example: Neurotic excoriations from habitual picking
FISSURE - Sharply defined linear or wedge-shaped tears in the epidermis with abrupt walls.
Example: Interdigital tinea pedis
PITS - Small, sharply demarcated depressions in the skin or nail surface.
Example: Pitted keratolysis
ULCER - A circumscribed loss of the epidermis and at least upper dermis. Ulcers are further classified by their depth, border, shape, edge, and the tissue at its base.
Example: Venous stasis ulcer
ABSCESS - A localized accumulation of pus in the dermis or subcutaneous tissue that is frequently red, warm, and tender.
Example: Methicillin-resistant Staphylococcus aureus (MRSA) infection
BULLA (PLURAL = BULLAE) - A large, raised, circumscribed blister that is greater than 10 mm* in diameter and is fluid filled. The fluid can be clear, serous, hemorrhagic, or purulent.
Example: Pemphigus vulgaris
CARBUNCLE - An inflammatory nodule composed of two or more confluent furuncles with separate heads.
Example: Staphylococcus aureus infection
CYST - A closed cavity or sac containing fluid or semisolid material. A cyst may have an epithelial or endothelial lining.
Example: Epidermal inclusion cyst
FURUNCLE - An acute, round, firm, circumscribed, follicle-centered nodule caused by infection that is usually greater than 10 mm in diameter. Characterized by pain, redness, and potentially visible pus.
Example: Staphylococcus aureus infection
PUSTULE - A purulent (pus filled) vesicle. Pustules are filled with neutrophils and may be white or yellow. Not all pustules are infected.
Example: Bacterial folliculitis
VESICLE - A small, superficial, circumscribed blister that is less than 10 mm* in diameter and is fluid filled. The fluid may be clear, serous, hemorrhagic, or purulent.
Example: Herpes zoster
ECCHYMOSIS (PLURAL = ECCHYMOSES) - Nonblanching, purpuric macules or patches greater than 3 mm in diameter due to extravasated blood in the skin. Color changes over time may go from blue-black to brown-yellow, or green before fading away.
Example: Bruise from blunt trauma
HEMATOMA - A collection of extravasated blood that is relatively or completely confined within a space. The blood is usually clotted (or partly clotted) and, depending on time, may manifest various degrees of organization and color.
Example: Postsurgical bleeding
PURPURA - Bleeding into the skin that results in violaceous (violet or purple) discoloration that varies according to its duration and does not blanch with pressure. Purpura includes petechiae and ecchymoses. When purpuric lesions are palpable, they represent vasculitis (vascular inflammation).
Example: Henoch-Schönlein purpura
PETECHIAE - Tiny, 1- to 2-mm (pinpoint to pinhead size) nonblanchable purpuric macules resulting from the rupture of small blood vessels. Color may be red, purple, or brown.
Example: Rocky Mountain spotted fever
TELANGIECTASIA - Small, superficial cutaneous blood vessels that become persistently visible because they are dilated.
Example: Erythrotelangiectatic rosacea
*Some authorities classify lesions using a 5-mm size designation.