Cyclin D1 and retinoblastoma protein in vulvar cancer and adjacent lesions

Abnormalities in the cell cycle are associated with tumorigenesis but have not yet been identified in squamous cell carcinoma (SCC) of the vulva or in adjacent vulvar lesions. The purpose of this study was to identify cell cycle protein expression (cyclin D1 and retinoblastoma protein [pRb]) in vulvar SCC and in adjacent potentially premalignant lesions: lichen sclerosis (LS), squamous cell hyperplasia (SH), and vulvar intraepithelial neoplasia (VIN). Using immunohistochemical techniques, 57 SCCs were analyzed with 19 adjacent areas showing LS, 13 showing SH, 11 VIN, and six normal epithelium. Fifty-one percent of SCCs showed abnormal cyclin D1 expression and 37% showed abnormal pRb. Abnormal cyclin D1 expression in the adjacent areas was as follows: 53% in LS, 31% in SH, 18% in VIN, and 0% in normal. Abnormal pRb expression was as follows: 42% in LS, 62% in SH, 46% in VIN, and 33% in normal. Only 10 lesions showed abnormal expression of both proteins. Abnormal expression of cyclin D1 in SCC was statistically significant compared with adjacent normal epithelium. In SCC lesions, abnormal cyclin D1 expression was associated with greater depth of invasion. Abnormal pRb in SCC was associated with poor tumor grade. Cyclin D1 and pRb are separately involved in the progression of vulvar cancer, and changes in the expression of these proteins may represent an early stage of malignant transformation in vulvar disease.