mm, depending on one's definition of a vesicle. Pustule: A pustule is a small elevation of the skin usually consisting of necrotic inflammatory cells. Cyst: A cyst is an epithelial-lined cavity. Wheal: A wheal is a rounded or flat-topped, pale red papule or plaque that is characteristically evanescent, disappearing within 24 to 48 hours. The temporary raised skin on the site of a properly delivered intradermal (ID) injection is also called a welt, with the ID injection process itself frequently referred to as simply "raising a wheal" in medical texts. Welts: Welts occur as a result of blunt force being applied to the body with elongated objects without sharp edges. Telangiectasia: A telangiectasia represents an enlargement of superficial blood vessels to the point of being visible. Burrow: A burrow appears as a slightly elevated, grayish, tortuous line in the skin, and is caused by burrowing organisms. Secondary lesions Scale: Dry or greasy laminated masses of keratin, they represent thickened stratum corneum. Crust: Dried sebum usually mixed with epithelial and sometimes bacterial debris Lichenification: Epidermal thickening characterized by visible and palpable thickening of the skin with accentuated skin markings Erosion: An erosion is a discontinuity of the skin exhibiting incomplete loss of the epidermis, a lesion that is moist, circumscribed, and usually depressed. Excoriation: A punctate or linear abrasion produced by mechanical means (often scratching), usually involving only the epidermis, but commonly reaching the papillary dermis Ulcer: An ulcer is a discontinuity of the skin exhibiting complete loss of the epidermis and often portions of the dermis. Fissure is a lesion in the skin that is usually narrow but deep. Induration is dermal thickening causing the cutaneous surface to feel thicker and firmer. Atrophy refers to a loss of skin, and can be epidermal, dermal, or subcutaneous. With epidermal atrophy, the skin appears thin, translucent, and wrinkled. Dermal or subcutaneous atrophy is represented by depression of the skin. Maceration: softening and turning white of the skin due to being consistently wet. Umbilication is formation of a depression at the top of a papule, vesicle, or pustule. Phyma: A tubercle on any external part of the body, such as in phymatous rosacea Configuration "Configuration" refers to how lesions are locally grouped ("organized"), which contrasts with how they are distributed (see next section). Agminate: in clusters Annular or circinate: ring-shaped Arciform or arcuate: arc-shaped Digitate: with finger-like projections Discoid or nummular: round or