To establish the true natural history of VIN III from literature data.

In a systematic review, data of women with VIN III indexed in several computer databases were pooled. The effect of treatment was correlated with recurrences and progression of VIN III.

Ninety-seven articles met the inclusion criteria. Data of 3322 patients were available. The mean age at diagnosis of VIN III was 46. This decreased over time, although not significantly (P = 0.08). Recurrences were seen as often after local excision as after vulvectomy. The percentage of recurrences was lower, but not absent, after free surgical margins than after involved surgical margins (P < 0.001). 6.5% of the 3322 patients progressed to an invasive vulvar carcinoma. Occult carcinomas were diagnosed in 3.2% of patients and 3.3% carcinomas were diagnosed during follow-up. The mean age at diagnosis of invasive vulvar carcinoma was 52 years. Nine percent of 88 untreated patients progressed in 12 to 96 months to invasive vulvar carcinoma. Only 1.2% of the 3322 patients showed complete regression, mostly during the first 10 months after diagnosis, 41% of which was related to pregnancy.

Evidence exists that VIN III may progress to invasive vulvar carcinoma. However, the available literature suggests that the progression rate to invasive vulvar carcinoma is low. The incidence of invasion as found in this systematic review is probably even too high, because overreporting of (micro)invasive cases cannot be excluded. Only a prospective registration using a standardized pathology examination will provide information about the real natural history of VIN III.