The ISSVD has attempted to separate dystrophic lesions from VIN in order to draw up a standard nomenclature based on histopathological characteristics so as to obtain comparable data. But the definition of the dysplastic evolutive possibilities of hyperplastic lesions is still an open problem. In this study 40% of VIN I, 100% of VIN II and 16.6% of VIN III were associated with hyperplastic lesions. 16.6% of VIN III were associated with sclerosing lichen. In this case, a hyperplastic phase could have been followed by a distrophic one since the patient was 73 years old. The overall frequency of cellular atypia in vulvar dystrophy was therefore 14.66%; it increased to 41.66% during the hyperplastic phase. The age of patients increased in parallel to the severity of lesions. No decrease in the mean age of incidence was noted except in those cases associated with HPV. The potential uncontrolled increase of hyperplastic alterations could have been produced by the absence of an inhibitory incidence stimulus, as has been noted in the resistance to topical steroid therapy in some cases of squamous hyperplasia. The localisation of cellular atypia, however, indicates surgical treatment.