Definition. Scars are connective tissue new-formations which replace, in the process of repair, a loss of substance extending into the corium or deeper tissues, and result from either accident or disease.
Scars may be either small or large, round, oval or irregularly shaped. Their shape is naturally determined by the form of the previous destruction or ulceration. They may be soft, smooth and pliable or occasionally thick, tough, uneven, stringy, puckered or even keloidal or hypertrophic. Scars are covered by an epithelial layer and consist of connective tissue which contains blood- vessels, lymphatics and nerves but no hairs or glandular structures unless the scars are very superficial. Scars usually follow active or neurotic tissue destruction but this is not invariably the rule. For example the superficial scars resulting from lupus vulgaris and syphilis are the result of absorption and non-ulcerative changes; the scars seen in atrophia cutis are the result of atrophy from distention and those in favus, of atrophy from pressure; occasionally scars are caused by neoplastic hypertrophy of the fibrous elements as in keloid; or scars may be hypertrophic from excessive formation of connective tissue as the result of deep ulcers or injuries. In the last instance they may be raised into ridges, elevated above the skin and attached to subjacent tissues as in false keloid.
At first, scars are pink or red in color and they may remain so for some time, later becoming purplish or pigmented. With age they usually become white from lessened blood supply and previous loss of the pigment layer. Scars may be of considerable diagnostic importance and for this purpose their location, shape, color, size, surface and mobility should be carefully noted. Exemplifying the diagnostic value of scars, it may be remarked that those of smallpox are usually numerous, small, scattered, pea-size, white and depressed, while those following the miliary papular or pustular syphilid are minute, pin-head-sized, scattered over the surface with a tendency to aggregation but scanty in number and usually rare on the face.