Histological responses of portwine stain vessels after dye laser exposure

Abstract

Improvement of laser technology enabled us to treat various kinds of color disorders of the skin. Compared to the other fields of medicine, cutaneous laser surgery has the following advantages; (1) The skin is a organ that exists on the surface of the body, which makes it easy to access from outside. So, the laser delivery system can be simple and easy to make. (2) The target of the skin color disorders is always “color”. So, some laser wavelength can be selected according to the 'color'of the lesion, in order to make the light absorbed selectively and to destroy the abnormal structure selectively. In 1983, Parrish and Anderson developed a new theory called selective photothermolysis. This theory pointed out a possibility to selectively destroy a certain structure within the skin without damaging surrounding structures using a laser light of the following quality; (1) The target structure has a higher absorption rate than the surrounding structures at the wavelength of the laser light. (2) The pulse duration is short enough for avoiding thermal diffusion before the target is completely damaged. Following this new theory, the flashlamp pumped dye laser (585nm/0.45ms) was made for treating cutaneous vascular lesions. We investigated histological responses against this laser and revealed its effectiveness. Although flashlamp pumped dye laser has become the first choice for treating portwine stains, its effectiveness is considered to have its own limitation. A new theory is advocated in which you can understand the histopathological reaction and prognostic diagnosis. Each kind of portwine stain vessels reacts as follows; In case of relatively less energy, coagulated blood dissolute again and the abnormal vessels remain intact (re-canalization). In case of enough energy, some large vessels suffer thermal damage and change to small neo-vessels (re-vascularization) or small vessels turn to be granulation tissue (vanishment). A new histological classification of portwine stain is advocated in which a clinical type is expressed by a combination of three vessel types; subepidermal, papillary and reticular vessels. On magnified inspection, subepidermal vessels look granular, papillary vessels look branching, and reticular vessels look even redness. This theory enables easy analysis for the structure of the portwine stain vessels, and furthermore, easy estimation of the prognosis after flashlamp dye laser exposure. More recently, a new type of lasers called Q-switched lasers was developed for treating dermal pigmented lesions. In near future, every kinds of skin color disorders may be treated by lasers.