Female patients with Lynch syndrome complicate with endometrial cancer at a high incidence. In the revised 1999 Amsterdam II Criteria (AC II), endometrial cancer was included as a cancer with similar features to colon, small intestine, ureteral and kidney cancers.[13] The prevalence of Lynch syndrome is 0.9–2.7%[14] and approximately 2.3% of cases of endometrial cancer occur due to Lynch syndrome.[15] The lifetime risk of endometrial cancer is 28–60% in women with aberrant genes associated with Lynch

syndrome.[16] hMLH1, hMSH2 and hMSH6 mutations are particularly Tanespimycin in vitro important in families of patients with Lynch syndrome. Most mutations occur in hMLH1 and hMSH2, whereas hMHS6 mutations are important in tumorigenesis in patients with endometrial cancer.[17, 18] Kawaguchi et al.[19] proposed a possible new cascade in which hMSH6 mutation is induced by silencing of hMLH1 due to aberrant DNA hypermethylation in endometrial cancer. Westin et al.[20] showed that the incidence of Lynch syndrome was 1.8% in endometrial cancer in total and 9% in endometrial cancer in Ku-0059436 nmr women aged less than 50 years old, but 29% in cases with lower uterine

segment cancer (LUS) and germ cell mutation of hMSH2. These results suggest a correlation between endometrial cancer of the uterine isthmus and Lynch syndrome. Masuda et al.[21] also found germ cell mutations of hMLH1 in 1.4% of patients with LUS. Based on these findings, Lynch syndrome may be

clinically predictive of the onset site of endometrial cancer. Several gene mutations have emerged as candidates for roles in carcinogenesis of type I and II endometrial cancer (Fig. 2), based on observation of the mutation in endometrial hyperplasia and at least a similar incidence of mutation in endometrial cancer. Different genes are involved in carcinogenesis of the two types of endometrial cancer. Gene mutations found in type I endometrial cancer include those in PTEN, β-catenin and cAMP K-ras. PTEN is a tumor suppressor gene on chromosome 10 and has been identified as a disease gene in three autosomal dominant disorders (Cowden disease, Lhermitte-Duclos disease and Bannayan-Zonana syndrome). PTEN inactivation is also found in malignant melanoma, brain tumors, and endometrial, ovarian, thyroid, breast and prostate cancers. PTEN protein induces apoptosis and carcinogenesis occurs in cells with PTEN mutation due to avoidance of apoptosis. PTEN mutations have been detected in 20–33% of cases of atypical endometrial hyperplasia and 33–50% of cases of endometrial cancer;[22-24] thus, PTEN appears to be involved in the early stage of carcinogenesis, which is a pattern that differs from that in late-onset cancer, including rectal cancer.