Differential expression patterns of GATA3 in usual and differentiated types of vulvar intraepithelial neoplasia: potential diagnostic implications

The two main precursors of vulvar squamous cell carcinoma, usual and differentiated vulvar intraepithelial neoplasia (VIN), have distinctive etiology, pathogenesis, and natural history. Usual type VIN is often associated with high-risk HPV and differentiated VIN has de novo p53 genetic alterations that are unrelated to HPV infection. GATA-binding protein 3 (GATA3) is a tumor suppressor that shows increased expression in several types of human malignancies including breast and bladder carcinomas. Little is known regarding the expression of GATA3 in vulvar squamous neoplasms. We have systematically examined the expression of GATA3 in 119 vulvar lesions and neoplasms including 20 cases of lichen sclerosus, 12 cases of lichen simplex chronicus, 30 cases of usual type VIN, 34 cases of differentiated VIN, and 23 cases of squamous cell carcinoma. Similar to adjacent non-neoplastic epidermis, moderate to strong GATA3 expression was retained in all cases of lichen sclerosus, lichen simplex chronicus, and usual type VIN. However, in comparison, the GATA3 immunostaining pattern in differentiated VIN was distinct. Partial/complete loss of GATA3 expression in the basal layer with or without loss in the parabasal layer was observed in 30/34 (88%) of differentiated VIN cases. Significant loss of GATA3 expression was also observed in all (7/7) squamous cell carcinomas associated with usual type VIN and in 13/16 (81%) of those associated with differentiated VIN. There was no significant correlation between loss of GATA3 expression and overexpression of p53 in differentiated VIN. Our study shows that loss of GATA3 expression is seen in the vast majority (87%) of vulvar squamous cell carcinomas. Downregulation of GATA3 may be an early event during tumorigenesis in differentiated VIN but not in HPV-related usual type VIN. Our data suggests that application of GATA3 immunohistochemistry along with p53 may be a useful tool in facilitating the accurate diagnosis of VIN.