Endometrial adenocarcinoma is a type of cancer that begins in the lining of the uterus and represents the most common gynecologic malignancy affecting women in the United States. While it may sound overwhelming to hear this diagnosis, understanding the disease can help patients and their families navigate the journey ahead with greater confidence and clarity.

Understanding Endometrial Adenocarcinoma

Endometrial adenocarcinoma is a cancer that starts in the endometrium, which is the inner lining of the uterus. The uterus itself is a hollow, pear-shaped organ in the pelvis where a fetus develops during pregnancy. The endometrium is the layer of tissue that thickens and sheds during the menstrual cycle in women who are still having periods.^[1]

When we talk about endometrial adenocarcinoma, we are specifically referring to cancers that begin in the glandular cells of the endometrium. The term adenocarcinoma means that the cancer originates in glandular tissue, which lines or covers internal organs. Most endometrial cancers fall into this category, making it the predominant form of uterine cancer that doctors encounter.^[6]

This type of cancer is sometimes also referred to as uterine cancer or endometrial carcinoma. However, it’s important to distinguish it from other types of uterine cancer, such as uterine sarcoma, which develops in the muscle wall of the uterus rather than the lining. Endometrial adenocarcinoma accounts for approximately 95% of all uterine cancer cases, while sarcomas are quite rare.^[4]

How Common Is This Condition

Endometrial cancer is the most prevalent gynecologic malignancy among women in the United States. It represents a significant health concern, with over 66,000 new cases expected in 2023 alone, and more than 13,000 deaths attributed to this cancer in the same year. When looking at all cancers affecting women, endometrial carcinomas account for approximately 7% of cases.^[3]

The lifetime risk for women developing uterine cancer is notable. About 3% of women will receive a diagnosis of uterine cancer at some point during their lives. Each year, approximately 65,000 women are diagnosed with this condition in the United States.^[4]

Of all the cases of endometrial cancer reported, more than 83% are adenocarcinomas originating from the endometrium. Other, more aggressive types such as serous and papillary serous carcinomas make up only 4% to 6% of endometrial carcinomas, while clear cell carcinomas represent just 1% to 2%.^[3]

Endometrial cancer primarily develops after menopause, meaning that older age is a significant factor in who is affected by this disease. The majority of women diagnosed with endometrial adenocarcinoma are postmenopausal, though it can occur in younger women as well.^[4]

What Causes Endometrial Adenocarcinoma

The exact cause of endometrial adenocarcinoma is not completely understood by researchers. What is known is that something triggers changes in the cells of the uterine lining. These changes cause the cells to become abnormal and begin to grow and multiply out of control. Over time, this uncontrolled growth can form a mass known as a tumor.^[4]

One of the most important factors in the development of endometrial cancer is prolonged exposure to the hormone estrogen without the balancing effect of another hormone called progesterone. Estrogen causes the endometrium to thicken, while progesterone helps to keep this growth in check. When there is too much estrogen or not enough progesterone, the endometrial lining can continue to grow excessively, potentially leading to abnormal changes in the cells. This hormone imbalance is often referred to as unopposed estrogen exposure.^[13]

Several situations can lead to this imbalance. For example, women who take estrogen-only hormone replacement therapy after menopause are at increased risk because they are not receiving progesterone to balance the effects of estrogen. On the other hand, taking estrogen combined with progesterone does not increase a woman’s risk of developing endometrial cancer.^[10]

Another medication that can increase risk is tamoxifen, which is used to prevent or treat breast cancer. Tamoxifen can have estrogen-like effects on the uterine lining, which may lead to endometrial cancer in some women. Women taking this drug who experience abnormal vaginal bleeding should have a follow-up exam and possibly a biopsy of the endometrial lining.^[10]

Who Is at Higher Risk

Certain groups of women face a higher likelihood of developing endometrial adenocarcinoma due to a variety of factors related to hormones, body weight, genetics, and reproductive history. Understanding these risk factors can help women and their healthcare providers stay vigilant about screening and prevention.

Increasing age is one of the most important risk factors for endometrial cancer, as it is for most types of cancer. The chance of developing cancer increases as a person gets older, with most cases of endometrial cancer occurring after menopause.^[13]

Obesity is a major risk factor for endometrial adenocarcinoma. Excess body fat can lead to higher levels of estrogen in the body because fat tissue can produce estrogen. This increased estrogen exposure over time raises the risk of developing cancer in the uterine lining. Women who have metabolic syndrome, a cluster of conditions that includes high blood pressure, high blood sugar, excess body fat around the waist, and abnormal cholesterol levels, are also at increased risk.^[10]

Women with type 2 diabetes have an elevated risk of endometrial cancer. Diabetes is often linked to obesity and metabolic syndrome, which contribute to the hormonal imbalances that can lead to cancer. Similarly, women with polycystic ovary syndrome (PCOS), a condition that causes irregular menstrual periods and hormone imbalances, are at greater risk because they often experience prolonged exposure to estrogen without progesterone.^[10]

Reproductive factors also play a role. Women who have never given birth, who started menstruating at an early age, or who went through menopause at a later age have had more lifetime exposure to estrogen. This longer exposure increases the risk of developing endometrial cancer.^[10]

Family history and genetics matter as well. Women who have a mother, sister, or daughter with endometrial cancer are at higher risk. Certain inherited genetic conditions, such as Lynch syndrome, significantly increase the likelihood of developing endometrial cancer. Lynch syndrome is a hereditary condition that raises the risk of several types of cancer, including colorectal and endometrial cancers.^[10]

Additionally, women who have endometrial hyperplasia, a condition where the endometrium becomes abnormally thick, are at increased risk. Endometrial hyperplasia can sometimes progress to cancer if not treated.^[10]

Recognizing the Symptoms

One of the most important aspects of endometrial adenocarcinoma is that it often causes noticeable symptoms early in the disease. This early warning system allows many women to seek medical attention before the cancer has spread, which can improve outcomes significantly.

The most common symptom of endometrial cancer is abnormal vaginal bleeding. For women who have gone through menopause, any vaginal bleeding or spotting is considered abnormal and should be evaluated by a healthcare provider. Even a small amount of bleeding after menopause can be a sign of endometrial cancer.^[1]

For women who have not yet gone through menopause, symptoms may include bleeding between periods or periods that are unusually heavy, prolonged, or frequent. Women over the age of 40 who experience these changes in their menstrual patterns should also seek medical advice.^[4]

Other symptoms that may occur include pelvic pain or cramping in the lower abdomen, just below the belly. Some women may also notice a thin, white, or clear vaginal discharge if they are postmenopausal. These symptoms can resemble those of other conditions affecting the reproductive organs, so it’s important to get an accurate diagnosis from a healthcare provider.^[4]

In more advanced stages of the disease, women may experience additional symptoms such as abdominal bloating, feeling full quickly when eating, or changes in bowel or bladder habits. These symptoms can indicate that the cancer has spread beyond the uterus.^[7]

Because many of the symptoms of endometrial cancer can also be caused by other, less serious conditions, it’s important not to panic but to seek medical evaluation promptly. Early detection and treatment can make a significant difference in outcomes.

Prevention and Reducing Your Risk

While it’s not possible to prevent endometrial adenocarcinoma entirely, there are steps women can take to reduce their risk. Many of these steps involve managing the factors that contribute to hormone imbalances and maintaining overall health.

Maintaining a healthy body weight is one of the most important ways to lower the risk of endometrial cancer. Because excess body fat increases estrogen levels, losing weight through a combination of healthy eating and regular physical activity can help reduce risk. Women who are overweight or obese should work with their healthcare providers to develop a safe and effective weight loss plan.^[4]

For women who are taking hormone replacement therapy after menopause, using a combination of estrogen and progesterone rather than estrogen alone can help protect the uterus. Women who still have a uterus should not take estrogen without progesterone, as this increases the risk of endometrial cancer. Those who have had a hysterectomy, however, can safely take estrogen alone because they no longer have a uterus.^[10]

Women who are taking tamoxifen for breast cancer should be aware of the increased risk of endometrial cancer and should report any abnormal vaginal bleeding to their healthcare provider immediately. Regular gynecologic exams and monitoring can help detect any problems early.^[10]

Using oral contraceptives, also known as birth control pills, has been shown to reduce the risk of endometrial cancer. The protective effect can last for many years after a woman stops taking the pill. Women should discuss the benefits and risks of oral contraceptives with their healthcare providers to determine if this option is right for them.

For women with a strong family history of endometrial cancer or those with Lynch syndrome, genetic counseling and testing may be recommended. These women may benefit from more frequent screening or preventive measures, such as a hysterectomy, to reduce their risk.^[10]

Finally, maintaining a healthy lifestyle that includes regular exercise, a balanced diet rich in fruits and vegetables, and avoiding smoking can contribute to overall health and may help reduce the risk of many types of cancer, including endometrial cancer.

How Endometrial Adenocarcinoma Affects the Body

Understanding how endometrial adenocarcinoma develops and progresses in the body can help patients grasp what is happening inside them and why certain treatments are recommended. The disease begins with changes at the cellular level in the lining of the uterus and can progress to affect other parts of the body if not detected and treated early.

The endometrium is a hormonally sensitive layer of tissue that responds to the rise and fall of estrogen and progesterone during the menstrual cycle. In reproductive-age women, estrogen causes the endometrium to thicken in preparation for a possible pregnancy. If pregnancy does not occur, progesterone levels drop, and the lining is shed during menstruation. After menopause, when hormone levels decline, the endometrium generally becomes thin and inactive.^[13]

In endometrial adenocarcinoma, the normal regulation of cell growth in the endometrium goes awry. Cells begin to divide uncontrollably, often due to prolonged exposure to estrogen without the counterbalancing effect of progesterone. This can lead to a thickening of the endometrial lining, known as endometrial hyperplasia, which in some cases can progress to cancer.^[13]

The cancer initially grows within the lining of the uterus, but over time, it can invade deeper into the muscular wall of the uterus. This is an important distinction because the depth of invasion affects the stage of the cancer and influences treatment decisions. The cancer can also spread to nearby structures, such as the cervix, vagina, and ovaries.^[7]

As endometrial cancer progresses, it can spread beyond the uterus to other parts of the body. This spread, known as metastasis, typically occurs through the lymphatic system or the bloodstream. Common sites of metastasis include the pelvic and abdominal lymph nodes, the bladder, rectum, bones, and lungs.^[7]

Endometrial cancer is staged from I to IV based on how far the cancer has spread. Stage I means the cancer is found only in the uterus. Stage II indicates that the tumor has spread from the uterus to the cervix but not beyond. Stage III means the cancer has spread beyond the uterus but is still within the pelvic area, often involving lymph nodes or nearby organs. Stage IV indicates that the cancer has metastasized to the bladder, rectum, or distant organs such as the lungs or bones.^[7]

The biological behavior of endometrial adenocarcinoma varies depending on its type and grade. Most endometrial cancers are classified as Type 1 cancers, which tend to be linked to excess estrogen and are generally slower growing and less likely to spread. Type 2 cancers, which are not linked to excess estrogen, are typically more aggressive and have a higher likelihood of spreading.^[6]

The grade of the cancer, which describes how much the cancer cells look like normal cells under a microscope, also plays a role in determining how the cancer behaves. Grade 1 cancers have cells that look very similar to normal cells and tend to grow slowly. Grade 2 cancers have cells that look somewhat abnormal, while Grade 3 cancers have cells that look very different from normal cells and are more likely to grow and spread quickly.^[6]