PATTERNS OF ALLELIC LOSS (LOH) IN VULVAR SQUAMOUS CARCINOMAS AND ADJACENT NONINVASIVE EPITHELIA

The pathogenesis of carcinoma of the vulva is diverse and includes bot h human papilloma virus (HPV)positive and HPV-negative pathways. The o bjective of this study was to correlate the morphology with patterns o f loss of heterozygosity (LOH) within four vulvar carcinomas and in ad jacent vulvar epithelia. Tumors were categorized as HPV positive or ne gative by polymerase chain reaction (PCR) analysis. Forty-one differen t sites of normal squamous mucosa, hyperplasia, vulvar intraepithelial neoplasia (VIN), and carcinoma were microdissected in duplicate, and each extracted DNA was analyzed in duplicate for LOH at 10 chromosomal loci by PCR and polyacrylamide gel electrophoresis. Patterns of LOH w ere compared within different sites of tumors and between the tumor an d the noninvasive epithelia, Of three tumors with multiple invasive fo ci analyzed, divergent patterns of LOH were identified in two, correla ting in one with differences in tumor grade. In one HPV-16-positive ca se, multiple sites of VIN displaced heterogeneity for LOH consistent w ith divergent clonal or subclonal populations, some of which were not shared by the tumor. In one HPV-negative case, LOH was found in foci o f hyperplasia and differentiated VIN (atypical hyperplasia), the latte r sharing LOH with the invasive carcinoma at some but not all chromoso mal loci. This study suggests that a genetic relationship exists betwe en VIN and carcinoma, irrespective of HPV involvement. It also suggest s that in HPV-negative tumors, allelic loss may predate the onset of i nvasive carcinoma and, in some cases, cellular atypia VIN). However, t he divergent patterns of LOH observed imply that many genetic alterati ons in the adjacent vulvar epithelium are not directly related to the invasive carcinoma.