Latent endometrial carcinoma precancers are normal-appearing endometrial glands with sporadic loss of tumor suppressor gene function such as PTEN. Progression to carcinoma is inefficient and requires additional genetic damage that creates a histologic precursor lesion called endometrial intraepithelial neoplasia (EIN). In this study, we examined loss of PAX2 expression, a gene required for embryonic uterine development, during endometrial carcinogenesis. Normal proliferative, EIN, and malignant (endometrial adenocarcinoma) endometrial tissues were immunostained for PTEN and PAX2. Proliferative samples with loss of protein in at least one gland were scored as latent precancers. EIN and cancer lesions were scored by the majority pattern. Overall prevalence and topography of joint PAX2-PTEN expression loss was examined. The prevalence of PAX2 protein loss in the sequence of normal to precancer to cancer was 36%, 71%, and 77%, respectively, and for PTEN, it was 49%, 44%, and 68%, respectively. The normal endometrial prevalence of PAX2-or PTEN-deficient latent precancers was unaffected by biopsy indication, but increased significantly with age. Coincident loss of PAX2 and PTEN expression in an individual normal endometrium was seen in 21% of patients, but usually involved different glands. Coincident loss was more common in precancers (31%) and carcinoma (55%), in which case, both markers were protein null in an overlapping clonal distribution. PAX2 and PTEN protein loss occurs independently and accumulates with increasing age in latent precancers of normal premenopausal endometrium. Loss of function of both genes in an overlapping distribution characterizes the clinical emergence of a premalignant lesion which is carried forward to carcinoma. Cancer Res; 70(15); 6225-32. ©2010 AACR.

Differentiated vulvar intraepithelial neoplasia is a unique precursor to vulvar squamous cell carcinoma that is typically HPV-negative and frequently associated with nuclear p53 staining. These features imply a mode of pathogenesis involving somatic mutations. However, the genetic relationship of differentiated vulvar intraepithelial neoplasm and vulvar squamous cell carcinoma and the role of Tp53 mutations in this process have not been resolved. We analyzed 11 differentiated vulvar intraepithelial neoplasms and 6 associated vulvar squamous cell carcinomas. Sections were stained for p53 and p63 and DNA from multiple epithelial sites, representing normal control tissues (n ¼ 10), differentiated vulvar intraepithelial neoplasias (n ¼ 18), and vulvar squamous cell carcinomas (n ¼ 6), were obtained by laser capture microdissection, and sequenced for exons 2-11 of Tp53. Six of 10 cases contained at least one Tp53 mutation-positive differentiated vulvar intraepithelial neoplasia focus; 4 strongly p53 immuno-positive and 2 negative. Staining for p53 and p63 co-localized, targeting the immature epithelium, but surface epithelium was Tp53 mutation-positive. Four of five vulvar squamous cell carcinomas were Tp53 mutation-positive; two shared identical Tp53 mutation with adjacent differentiated vulvar intraepithelial neoplasia. Disparate foci of differentiated vulvar intraepithelial neoplasia often showed different mutations consistent with multiple neoplastic clones. Differentiated vulvar intraepithelial neoplasia is, with few exceptions, associated with Tp53 mutations and will be p53 immunopositive when missense mutations (versus some nonsense and all deletion mutations) are present. Multiple Tp53 mutations in different sites supports the presence of multiple independent genetic events, but shared Tp53 mutations in both differentiated vulvar intraepithelial neoplasia and vulvar squamous cell carcinoma support a genetic relationship between the two. The confinement of p53 staining to immature cell nuclei is consistent with maturation-dependent degradation of mutant p53 protein.