A hemangioma or vascular nevus is a congenital new growth and hypertrophy of the blood vessels of the skin. Small telangiectases are frequently acquired, but the larger lesions are always congenital. Unna is inclined to believe that external pressure during intrauterine life is responsible, while still others have thought that nerve changes might be responsible, inasmuch as they frequently develop along the distribution of a nerve.
Several groups must be recognized. First, the small telangiectatic spots; second, the flat nevi; third, the nevi containing spongy tissue of a somewhat erectile character and that protrudes considerably above the surface of the skin; and fourth, the racemose aneurysms. The second class usually remain stationary, but the members of the other three groups may grow to a considerable extent, so should always be kept under observation. Occasionally a sarcoma may develop from one of these lesions.
The smaller telangiectases can be removed, if this be considered advisable, by either the electric needle or by carbon dioxide snow. The pale flat nevi should be left alone, and even the dark ones are difficult to handle satisfactorily, although many claims have been made for the Kromayer lamp, claims that not all dermatologists are willing to concede. Eadium is not satisfactory, as it acts by producing scar tissue. Mild freezing with carbon dioxide snow is at times beneficial. The large protruding nevi are probably best treated by means of the snow, this being undoubtedly much better than injections of boiling water or scarification with the cautery. The racemose aneurysms should be treated by surgical methods.