Rectosigmoid cancer develops at the junction where the sigmoid colon meets the rectum, creating unique challenges in both diagnosis and treatment. This form of colorectal cancer sits in a gray area between typical colon and rectal cancers, and understanding its specific characteristics is essential for effective care.
Understanding Rectosigmoid Cancer
Rectosigmoid cancer is a type of colorectal cancer that forms in the area where the sigmoid colon transitions into the rectum. The sigmoid colon is the last curved portion of your colon before it connects to the rectum. This location matters because it affects how doctors approach treatment. While colon and rectal cancers share many similarities, the treatments can be quite different depending on exactly where the tumor sits in your digestive system.[1]
Your rectum is the final several inches of your large intestine. It ends at the anus, which is the opening through which waste leaves your body. The rectum sits in a tight space in your pelvis, closely surrounded by other organs and structures. This makes surgery more complex compared to removing tumors from other parts of the colon that have more room around them.[2]
The location where the sigmoid colon meets the rectum typically falls between 9 and 20 centimeters from the anal opening. Doctors measure this distance during examinations to help determine the best treatment approach. An important anatomic marker called the peritoneal reflection helps doctors decide whether to treat a tumor more like rectal cancer or sigmoid colon cancer. The peritoneal reflection is a fold of the membrane that lines your abdominal cavity.[1]
How Common Is Rectosigmoid Cancer
Colorectal cancer, which includes cancers of both the colon and rectum, ranks as the fourth most common type of cancer. When looking at digestive system cancers specifically, rectal cancer is the third most common, following colon cancer and pancreatic cancer. Healthcare providers estimate that about 46,200 people will receive a diagnosis of rectal cancer in 2024.[14]
Males are slightly more likely to develop colorectal cancer than females. There are also differences across ethnic and racial groups. People who are Black face higher rates of colorectal cancer compared to members of other ethnic groups or races. The reasons behind these disparities remain under investigation by medical researchers.[5]
Colorectal cancer has traditionally affected people age 50 and older, with the average age of diagnosis being 63. However, a concerning trend has emerged over the past 15 years. The number of people between ages 20 and 49 diagnosed with colorectal cancer has been increasing by about 1.5 percent each year. Medical researchers are working to understand why younger adults are developing this disease more frequently.[5][14]
What Causes Rectosigmoid Cancer
Rectosigmoid cancer typically begins with small growths called polyps that form on the inner lining of the colon or rectum. Not all polyps turn into cancer, but some types have the potential to become cancerous over time. The transformation from a normal polyp into a cancerous tumor usually takes about 10 to 15 years. This slow progression is why screening tests are so effective at preventing cancer when they catch and remove polyps early.[4][14]
Colorectal cancer develops when cells in the colon or rectum begin to grow out of control. This happens because of certain changes in how these cells function, particularly in how they grow and divide to create new cells. Many risk factors for colorectal cancer don’t directly cause the disease but instead increase the chance of DNA damage in cells that may eventually lead to cancer.[7]
Cancer starts in the innermost lining of the colon or rectum, which consists of cells that make and release mucus and other fluids. When these cells mutate or change, they may create a polyp. If this polyp isn’t detected and removed, it can work its way through layers of tissue and muscle. Eventually, the cancer may spread to other parts of the body through the lymph nodes or blood vessels.[5]
Risk Factors That Increase Your Chances
Several factors can increase your likelihood of developing rectosigmoid cancer. Understanding these risk factors helps you and your doctor decide when to begin screening and how closely to monitor your health.
Family history plays a significant role in colorectal cancer risk. Having a first-degree relative, such as a parent, sibling, or child, with a history of colon or rectal cancer nearly doubles your chance of developing the disease. If you have a biological family member who has been diagnosed, make sure to discuss this with your healthcare provider.[7][14]
Your personal medical history also matters. If you’ve previously had colon, rectal, or ovarian cancer, you face increased risk. People with a history of high-risk adenomas—polyps that are 1 centimeter or larger or that have cells looking abnormal under a microscope—also have greater risk. Additionally, having chronic inflammatory bowel diseases like ulcerative colitis or Crohn’s disease for 8 years or more increases your chances of developing colorectal cancer.[7]
Certain inherited genetic conditions significantly raise colorectal cancer risk. These include familial adenomatous polyposis (FAP), Lynch syndrome (also called hereditary nonpolyposis colorectal cancer), MUTYH-associated polyposis, juvenile polyposis syndrome, Peutz-Jeghers syndrome, and PTEN hamartoma tumor syndrome. People with these conditions often need to start screening at younger ages and may require more frequent monitoring.[7][14]
Lifestyle factors contribute to colorectal cancer risk as well. Smoking cigarettes increases not only the risk of developing the disease but also the likelihood of dying from rectal cancer. Heavy alcohol consumption, defined as three or more drinks per day, raises risk. Eating a lot of red meat and processed meat has been linked to higher rates of colorectal cancer. People who have obesity face greater risk compared to those maintaining a healthy weight.[7][14]
Recognizing the Symptoms
Rectosigmoid cancer often doesn’t cause symptoms in its early stages. You can have cancer for years without noticing any changes in your body. This is precisely why screening tests are so important—they can detect cancer before symptoms appear, when treatment is most effective. However, as the cancer grows or becomes more advanced, certain warning signs may develop.[2]
One of the most common symptoms is blood in your stool or rectal bleeding. You might notice bright red or dark maroon blood on the toilet paper after wiping, blood in the toilet bowl, or stool that looks darker than usual. It’s important to remember that blood in stool doesn’t automatically mean cancer. Other conditions like hemorrhoids, anal tears, or even certain foods can cause changes in stool appearance. However, you should always check with a healthcare provider any time you notice blood in or on your stool.[2][5]
Changes in bowel habits are another key symptom to watch for. This includes new or persistent constipation, diarrhea, or a more frequent need to pass stool. Some people feel as though their bowel doesn’t empty completely even after using the bathroom. You might also notice that your stool looks different—perhaps narrower or stringier than usual, sometimes described as looking like a pencil.[2][5]
Abdominal or belly pain with no known cause that doesn’t go away or gets worse should prompt a conversation with your doctor. Many things can cause belly pain, but unusual or persistent discomfort warrants medical attention. Similarly, bloating that lasts for more than a week or progressively worsens deserves evaluation.[2][5]
General symptoms like unexplained weight loss, persistent tiredness or weakness, and loss of appetite can occur as colorectal cancer advances. Some people may also develop anemia from ongoing blood loss. During a medical examination, a doctor might detect a lump in the rectum.[2]
How to Lower Your Risk
While you cannot change certain risk factors like your age or family history, you can take steps to reduce your overall risk of developing rectosigmoid cancer through lifestyle modifications and regular screening.
If you smoke, quitting is one of the most important steps you can take. Smoking increases your risk of developing colorectal cancer and makes it more likely that you’ll die from the disease. Support programs are available to help you quit successfully.[20]
Limiting alcohol intake helps reduce risk. Heavy drinking has been linked to increased rates of colorectal cancer. Healthcare providers advise consuming alcohol only in moderation or not at all.[20]
Diet plays an important role in colorectal cancer prevention. Eating a healthy diet rich in fruits, vegetables, and whole grains while limiting red and processed meats may help lower your risk. High intake of red and processed meats has been shown to increase the likelihood of developing colorectal cancer.[20]
Regular physical activity has been linked to reduced colorectal cancer risk. An active lifestyle benefits your overall health in many ways, including potential cancer prevention. Talk with your doctor about an exercise program that’s appropriate for your current fitness level and health status.[20]
Maintaining a healthy body weight is another protective factor. Being overweight or having obesity increases your risk of colorectal cancer. Eating healthfully and exercising regularly can help you achieve and maintain a healthy weight.[20]
The most effective prevention strategy is regular screening. Colorectal cancer is unique because screening tests can both detect cancer early and actually prevent cancer from developing. Tests like colonoscopy can identify and remove polyps before they turn cancerous. Most people at average risk should start screening at age 45. People with certain risk factors may need to begin screening at younger ages. Discuss with your doctor when you should start screening and which test is right for you.[4][20]
How the Disease Develops in the Body
Understanding what happens inside your body when rectosigmoid cancer develops can help you better grasp why certain symptoms occur and how treatments work.
The wall of your colon and rectum consists of several layers. The innermost layer is the mucosa, which is made of cells that produce and release mucus and other fluids. When these cells undergo changes or mutations, they may form a polyp. Over time, some of these polyps can develop into cancer.[5]
As cancer develops, it begins growing through the different layers of the intestinal wall. It starts in the mucosa and can gradually work its way through underlying tissue, then through muscle layers, and eventually to the outer layer. If the cancer continues growing unchecked, it may break through the wall entirely and spread to nearby organs and structures.[5]
The rectum sits in a particularly tight space within the pelvis, barely separated from other organs. This close proximity to surrounding structures is one reason why rectal cancer presents unique treatment challenges. Surgery to remove rectal cancer can be complex because of the limited room for maneuvering surgical instruments.[2]
Cancer cells can also spread beyond the original tumor site through two main pathways. The lymphatic system, which includes lymph nodes throughout your body, provides one route. Cancer cells may break away from the original tumor and travel through lymph vessels to nearby lymph nodes. From there, they can spread to more distant lymph nodes and organs. Cancer cells can also enter blood vessels and travel through the bloodstream to reach distant parts of the body.[5]
Treatment approaches for rectosigmoid cancer depend heavily on the tumor’s exact location. Research has shown that tumors located below the peritoneal reflection—an anatomic landmark visible on medical imaging—may benefit from different treatment timing compared to tumors located above this line. Doctors use imaging studies to identify this landmark and help guide treatment decisions.[1]
The distance from the tumor to the anal opening also influences treatment planning. Tumors in the rectosigmoid region typically fall between 9 and 20 centimeters from the anal verge. Doctors measure this distance during colonoscopy and on imaging studies. These measurements, combined with information about the peritoneal reflection, help determine whether to approach treatment more like rectal cancer or more like sigmoid colon cancer.[1]