ABSTRACT
<p><b>OBJECTIVE</b>To investigate the clinical, pathological and immunohistochemical features of vulvar intraepithelial neoplasia (VIN).</p><p><b>METHODS</b>According to the 2004 modified terminology of International Society for the Study of Vulvovaginal Diseases (ISSVD), the cases were diagnosed as VIN from patients who had performed vulvar biopsy in Beijing Wuzhou Women's Hospital from February 2009 to December 2011, which were reclassified as usual VIN and differentiated VIN. The clinical and pathological studies were conducted respectively. MaxVision immunohistochemical staining was used to detect the expression of Ki-67, p16 and p53 proteins.</p><p><b>RESULTS</b>There were 20 cases of VIN in 237 patients, and the incidence of VIN was 8.4% in all of contemporary vulvar biopsy. In 17 cases of usual VIN, mean age was 29.6 years, the lesion typically presented with atypical cells involving almost all layers of the epithelium, which was equivalent to the high-grade squamous intraepithelial neoplasia of cervix. Immunohistochemistry for Ki-67 and p16 was strongly positive in usual VIN. High risk human papillomavirus (HPV) detection was also positive. The incidence of differentiated VIN was less than usual VIN, and there were only 3 cases in this study. In differentiated VIN, patients aged over 50 years, with mean of 53.7 years, and the lesion most commonly presented with lichen sclerosis background. There were epithelial thickening and extending, and parakeratosis, and atypia was strictly confined to the basal and parabasal layers of the epithelium where the cells enlarged with abundant eosinophilic cytoplasm, presented with prominent nucleoli, increased cellularity and abnormal keratinization. In differentiated VIN, p53 was strongly positive, Ki-67 and p16 immunohistochemical expression was confined to the basal layer only.</p><p><b>CONCLUSIONS</b>VIN is a precursor of invasive squamous cell carcinoma of the vulva. The modified terminology of ISSVD classifies VIN as high-grade lesions. Definitive pathological diagnosis of VIN plays an important role in its timely treatment and the prevention of vulvar carcinoma.</p>