Tissue Interaction When the laser beam contacts tissue, its energy is absorbed by the water in the cells, causing it to boil instantly. The cells explode into a puff of vapor (thus the term laser vaporization). The protein and mineral content is incinerated by the heat and leaves a charred appearance at the base of the exposed area. The depth of laser destruction is a function of the power of the beam (in watts), the area of the beam (in millimeters squared), and the length of time the laser remains in the tissue. The beam must be moved uniformly across the tissue surface to prevent deep destruction. The laser beam vaporizes a central area and leaves a narrow zone of heat necrosis surrounding the laser crater. The goal of laser vaporization is to minimize the area of tissue necrosis. This goal is accomplished by using high wattage (20 watts) with medium beam size (1.5 mm) and moving the beam uniformly but quickly over the surface. The zone of thermal necrosis will be 0.1 mm when the laser is used in this manner. Some lasers have a function called super pulse, in which the laser beam is electronically switched off and on thousands of times per second, thereby allowing the tissue to cool between pulses to create less thermal necrosis.
CHAPTER 19 Intraepithelial Disease of the Cervix, Vagina, and Vulva
Figure 19.18 A: Vaginal intraepithelial neoplasia grade 2 (VAIN 2). B: Vaginal intraepithelial neoplasia grade 3 (VAIN 3).
Cryosurgery should not be used in the vagina because the depth of injury cannot be controlled and inadvertent injury to the bladder or rectum may occur. Superficial fulguration with electrosurgical ball cautery may be used under colposcopic control to observe the depth of destruction by wiping away the epithelial tissue as it is ablated. Excision is an excellent method for treatment of upper vaginal lesions in a small area. Occasionally, total vaginectomy will be required for a VAIN 3 lesion occupying the entire vagina. It should be accompanied by a split-thickness skin graft. This aggressive treatment for widespread vaginal lesions should not be used for VAIN 2.
The malignant potential of VAIN appears to be less than that of CIN. In a review of 136 cases of CIS of the vagina over a 30-year period, 4 cases (3%) progressed to invasive vaginal cancer despite the use of various treatment methods (134).
Vulvar Dystrophies In the past, terms such as leukoplakia, lichen sclerosis et atrophicus, primary atrophy, sclerotic dermatosis, atrophic and hyperplastic vulvitis, and kraurosis vulvae were used to denote disorders of epithelial growth and differentiation (136). In 1966, Jeffcoate suggested that these terms did not refer to separate disease entities because their macroscopic and microscopic appearances were variable and interchangeable (137). He assigned the generic term chronic vulvar dystrophy to the entire group of lesions.
The International Society for the Study of Vulvar Disease (ISSVD) recommended that the old dystrophy terminology be replaced by a new classification under the pathologic heading nonneoplastic epithelial disorders of skin and mucosa. This classification is shown in Table 19.13. In all cases, diagnosis requires biopsy of suspicious-looking lesions, which are best detected by careful inspection of the vulva in a bright light aided, if necessary, by a magnifying glass (138).
The malignant potential of these nonneoplastic epithelial disorders is low, particularly now that the lesions with atypia are classified as VIN. Patients with lichen sclerosis and concomitant hyperplasia may be at particular risk (139).