Endometrial cancer

Endometrial cancer is a cancer that arises from the endometrium. It is the result of the abnormal growth of cells that can invade or spread to other parts of the body. The first sign is most often vaginal bleeding not associated with a menstrual period. Other symptoms include pain with urination, pain during sexual intercourse, or pelvic pain. Endometrial cancer occurs most commonly after menopause.
Approximately 40% of cases are related to obesity. Endometrial cancer is also associated with excessive estrogen exposure, high blood pressure and diabetes. Whereas taking estrogen alone increases the risk of endometrial cancer, taking both estrogen and a progestogen in combination, as in most birth control pills, decreases the risk. Between two and five percent of cases are related to genes inherited from the parents. Endometrial cancer is sometimes called "uterine cancer", although it is distinct from other forms of cancer of the uterus such as cervical cancer, uterine sarcoma, and trophoblastic disease. The most frequent type of endometrial cancer is endometrioid carcinoma, which accounts for more than 80% of cases. Endometrial cancer is commonly diagnosed by endometrial biopsy or by taking samples during a procedure known as dilation and curettage. A pap smear is not typically sufficient to show endometrial cancer. Regular screening in those at normal risk is not called for.
The leading treatment option for endometrial cancer is abdominal hysterectomy, together with removal of the Fallopian tubes and ovaries on both sides, called a bilateral salpingo-oophorectomy. In more advanced cases, radiation therapy, chemotherapy or hormone therapy may also be recommended. If the disease is diagnosed at an early stage, the outcome is favorable, and the overall five-year survival rate in the United States is greater than 80%.
In 2012, endometrial cancers newly occurred in 320,000 women and caused 76,000 deaths. This makes it the third most common cause of death in cancers which only affect women, behind ovarian and cervical cancer. It is more common in the developed world and is the most common cancer of the female reproductive tract in developed countries. Rates of endometrial cancer have risen in several countries between the 1980s and 2010. This is believed to be due to the increasing number of elderly people and rising obesity rates.

Signs and symptoms

or spotting in women after menopause occurs in 90% of endometrial cancer. Bleeding is quite common with adenocarcinoma, occurring in two-thirds of all cases. Abnormal menstrual cycles or extremely long, heavy, or frequent episodes of bleeding in women before menopause may also be a sign of endometrial cancer.
Symptoms other than bleeding are not common. Other symptoms include thin white or clear vaginal discharge in postmenopausal women. More advanced disease shows more obvious symptoms or signs that can be detected on a physical examination. The uterus may become enlarged or the cancer may spread, causing lower abdominal pain or pelvic cramping. Painful sexual intercourse or painful or difficult urination are less common signs of endometrial cancer. The uterus may also fill with pus. Of women with these less common symptoms, 10–15% have cancer.

Risk factors

Risk factors for endometrial cancer include obesity, insulin resistance and diabetes mellitus, breast cancer, use of tamoxifen, never having had a child, late menopause, high levels of estrogen, and increasing age. Immigration studies, which examine the change in cancer risk in populations moving between countries with different rates of cancer, show that there is some environmental component to endometrial cancer. These environmental risk factors are not well characterized. It is found that adiposity is associated with the earlier diagnosis of EC, particularly the endometrioid subtype.

Hormones

Most of the risk factors for endometrial cancer involve high levels of estrogens. An estimated 40% of cases are thought to be related to obesity. In obesity, the excess of adipose tissue increases conversion of androstenedione into estrone, an estrogen. Higher levels of estrone in the blood causes less or no ovulation and exposes the endometrium continuously to high levels of estrogens. Obesity also causes less estrogen to be removed from the blood. Polycystic ovary syndrome, which also causes irregular or no ovulation, is associated with higher rates of endometrial cancer for the same reasons as obesity. Specifically, obesity, type II diabetes, and insulin resistance are risk factors for Type I endometrial cancer. Obesity increases the risk for endometrial cancer by 300–400%.
Estrogen replacement therapy during menopause when not balanced with progestin is another risk factor. Higher doses or longer periods of estrogen therapy have higher risks of endometrial cancer. Women of lower weight are at greater risk from unopposed estrogen. A longer period of fertility—either from an early first menstrual period or late menopause—is also a risk factor. Unopposed estrogen raises an individual's risk of endometrial cancer by 2–10 fold, depending on weight and length of therapy. In trans men who take testosterone and have not had a hysterectomy, the conversion of testosterone into estrogen via androstenedione may lead to a higher risk of endometrial cancer. Higher circulating testosterone levels in women have also been identified as an independent endometrial cancer risk factor.

Genetics

s can also cause endometrial cancer. Overall, hereditary causes contribute to 2–10% of endometrial cancer cases. Lynch syndrome, an autosomal dominant genetic disorder that mainly causes colorectal cancer, also causes endometrial cancer, especially before menopause. Women with Lynch syndrome have a 40–60% risk of developing endometrial cancer, higher than their risk of developing colorectal or ovarian cancer. Ovarian and endometrial cancer develop simultaneously in 20% of people. Endometrial cancer nearly always develops before colon cancer, on average, 11 years before. Carcinogenesis in Lynch syndrome comes from a mutation in MLH1 or MLH2: genes that participate in the process of mismatch repair, which allows a cell to correct mistakes in the DNA. Other genes mutated in Lynch syndrome include MSH2, MSH6, and PMS2, which are also mismatch repair genes. Women with Lynch syndrome represent 2–3% of endometrial cancer cases; some sources place this as high as 5%. Depending on the gene mutation, women with Lynch syndrome have different risks of endometrial cancer. With MLH1 mutations, the risk is 54%; with MSH2, 21%; and with MSH6, 16%.
Women with a family history of endometrial cancer are at higher risk. Two genes most commonly associated with some other women's cancers, BRCA1 and BRCA2, do not cause endometrial cancer. There is an apparent link with these genes. It is attributable to the use of tamoxifen, a drug that itself can cause endometrial cancer, in breast and ovarian cancers. The inherited genetic condition Cowden syndrome can also cause endometrial cancer. Women with this disorder have a 5–10% lifetime risk of developing endometrial cancer, compared to the 2–3% risk for unaffected women.
Common genetic variation has also been found to affect endometrial cancer risk in large-scale genome-wide association studies. Sixteen genomic regions have been associated with endometrial cancer and the common variants explain up to 7% of the familial relative risk.

Protective factors

and the use of progestin are both protective against endometrial cancer. Smoking protects by altering the metabolism of estrogen and promoting weight loss and early menopause. This protective effect lasts long after smoking is stopped. Progestin is present in the combined oral contraceptive pill and the hormonal intrauterine device. Combined oral contraceptives reduce risk more the longer they are taken: by 56% after four years, 67% after eight years, and 72% after twelve years. This risk reduction continues for at least fifteen years after contraceptive use has been stopped. Obese women may need higher doses of progestin to be protected. Having had more than five infants is also a protective factor, and having at least one child reduces the risk by 35%. Breastfeeding for more than 18 months reduces risk by 23%. Increased physical activity reduces an individual's risk by 38–46%. There is preliminary evidence that consumption of soy is protective. Mendelian randomization analyses have established potential protective factors such as LDL cholesterol, later age of menarche and sex hormone binding globulin.

Pathophysiology

Endometrial cancer forms when there are errors in normal endometrial cell growth. Usually, when cells grow old or get damaged, they die, and new cells take their place. Cancer starts when new cells form unneeded, and old or damaged cells do not die as they should. The buildup of extra cells often forms a mass of tissue called a growth or tumor. These abnormal cancer cells have many genetic abnormalities that cause them to grow excessively.
In 10–20% of endometrial cancers, mostly Grade 3, mutations are found in a tumor suppressor gene, commonly p53 or PTEN. In 20% of endometrial hyperplasias and 50% of endometrioid cancers, PTEN has a loss-of-function mutation or a null mutation, making it less effective or completely ineffective. Loss of PTEN function leads to up-regulation of the PI3k/Akt/mTOR pathway, which causes cell growth. The p53 pathway can either be suppressed or highly activated in endometrial cancer. When a mutant version of p53 is overexpressed, the cancer tends to be particularly aggressive. P53 mutations and chromosome instability are associated with serous carcinomas, which tend to resemble ovarian and Fallopian carcinomas. Serous carcinomas are thought to develop from endometrial intraepithelial carcinoma.
PTEN and p27 loss of function mutations are associated with a good prognosis, particularly in obese women. The Her2/neu oncogene, which indicates a poor prognosis, is expressed in 20% of endometrioid and serous carcinomas. CTNNB1 mutations are found in 14–44% of endometrial cancers and may indicate a good prognosis, but the data is unclear. Beta-catenin mutations are commonly found in endometrial cancers with squamous cells. FGFR2 mutations are found in approximately 10% of endometrial cancers, and their prognostic significance is unclear. SPOP is another tumor suppressor gene found to be mutated in some cases of endometrial cancer: 9% of clear cell endometrial carcinomas and 8% of serous endometrial carcinomas have mutations in this gene.
Type I and Type II cancers tend to have different mutations involved. ARID1A, which often carries a point mutation in Type I endometrial cancer, is also mutated in 26% of clear cell carcinomas of the endometrium and 18% of serous carcinomas. Epigenetic silencing and point mutations of several genes are commonly found in Type I endometrial cancer. Mutations in tumor suppressor genes are common in Type II endometrial cancer. PIK3CA is commonly mutated in both Type I and Type II cancers. In women with Lynch syndrome-associated endometrial cancer, microsatellite instability is common.
Development of an endometrial hyperplasia is a significant risk factor because hyperplasias can and often do develop into adenocarcinoma, though cancer can develop without the presence of a hyperplasia. Within ten years, 8–30% of atypical endometrial hyperplasias develop into cancer, whereas 1–3% of non-atypical hyperplasias do so. An atypical hyperplasia is one with visible abnormalities in the nuclei. Pre-cancerous endometrial hyperplasias are also referred to as endometrial intraepithelial neoplasia. Mutations in the KRAS gene can cause endometrial hyperplasia and therefore Type I endometrial cancer. Endometrial hyperplasia typically occurs after the age of 40. Endometrial glandular dysplasia occurs with an overexpression of p53, and develops into a serous carcinoma.