Colon cancer is one of the most common cancers worldwide and a leading cause of cancer-related deaths. Early stages of colon cancer often cause no noticeable problems, so understanding the potential symptoms is crucial. This article outlines 15 key symptoms of colon cancer and explains the stages of the disease, from early (localized) cancer to advanced (metastatic) cancer. Each symptom and stage is described in a professional yet accessible tone, with details on how symptoms may progress as the cancer advances and how doctors determine the cancer’s stage.
1. Persistent Diarrhea
Ongoing or recurrent diarrhea (loose, watery stools) that lasts more than a few days can be a symptom of colon cancer. Many people experience short bouts of diarrhea due to diet or minor illnesses, but diarrhea that does not go away or keeps coming back without a clear cause is concerning. A colon tumor can disrupt normal bowel function, leading to more frequent and loose bowel movements. If you notice prolonged diarrhea (especially if it lasts for weeks), it’s important to talk to a healthcare provider. Chronic diarrhea can also contribute to dehydration and weakness.
2. Chronic Constipation
Difficulty having bowel movements or infrequent stools (constipation) that persists can also signal a problem. A tumor in the colon can partially block the passage of stool, making it hard to pass stool or causing a feeling of being “backed up.” Occasional constipation is common, but persistent constipation or a significant change from your normal bowel pattern should be investigated. In some cases, people might have the urge to move their bowels but produce only small amounts of stool. Long-term constipation can cause discomfort, bloating, and even contribute to hemorrhoids, so it’s important to identify the underlying cause.
3. Narrow or Ribbon-Like Stools
Noticeable changes in the shape or caliber of your stool – for example, stool becoming very thin like a ribbon or pencil – could be a symptom of colon cancer. A growing tumor in the colon, especially in the lower part, can narrow the passageway. As a result, the stool may squeeze through in a thin, narrowed form. Everyone’s stool size can vary, but if you observe a persistent change to thinner stools, it could indicate an obstruction in the colon. This symptom is often grouped with changes in bowel habits and should not be ignored if it lasts more than a few days.
4. Feeling of Incomplete Evacuation (Tenesmus)
Tenesmus is the sensation of not fully emptying your bowels, even after you’ve just had a bowel movement. In colon cancer, people may feel a constant urge to have a bowel movement that isn’t relieved by doing so. Essentially, you might go to the bathroom and then soon feel like you need to go again, or you may sit on the toilet feeling like there is more stool to pass even when there isn’t. This occurs because a tumor in the rectum or lower colon can create the false impression that there is something still in the bowel. If you frequently feel “unfinished” after bowel movements, discuss it with your doctor.
5. Rectal Bleeding (Bright Red Blood)
Seeing bright red blood on the toilet paper or in the toilet bowl after a bowel movement is a alarming symptom that can be caused by colon cancer (though it can also stem from benign issues like hemorrhoids). In colon cancer, bright red blood typically suggests bleeding in the lower part of the colon or rectum. You might notice streaks of red blood on the surface of the stool or just blood by itself. Any rectal bleeding, especially if it’s recurrent, heavy, or combined with other symptoms, should be evaluated. While hemorrhoids are a common cause of red blood in stool, it’s critical not to assume bleeding is just hemorrhoids without proper medical examination.
6. Dark or Tarry Stool (Blood in Stool)
Not all blood in the stool is bright red; blood coming from higher up in the colon can make stool appear dark brown, black, or tarry in appearance. A tumor on the right side or deeper in the colon often bleeds slowly, and by the time the blood travels through the intestines, it dries and darkens. This can result in stool that looks very dark or even black and sticky (sometimes described as “tar-like”). Such stool, called melena, indicates digested blood. If you notice unusually dark or black stools (that aren’t explained by iron supplements or foods like black licorice or blueberries), it could signal internal bleeding in the GI tract. A fecal occult blood test done by a doctor can detect hidden blood in stool even when you can’t see it.
7. Abdominal Cramping or Pain
Cramping, aching, or persistent pain in the lower abdomen can be one of the symptoms of colon cancer. You might experience pain or discomfort in your belly that doesn’t have an obvious cause (such as indigestion or menstrual cramps). As a colon tumor grows, it can cause pain by pressing into the walls of the intestine or even partially blocking the bowel. The pain might come and go at first, often mistaken for gas pains or a stomachache. Over time, abdominal pain may become more frequent or severe as the cancer advances. Any unexplained belly pain that lasts for more than a few days or is worsening should be checked by a healthcare provider.
8. Bloating, Fullness, or Excessive Gas
Many colon cancer patients report a persistent feeling of bloating or fullness in the abdomen. You might notice that your stomach feels swollen or full of gas even after a normal meal. This bloating can be accompanied by excessive gas or frequent belching. A tumor can slow down digestion and cause gas to build up behind it, leading to chronic bloating or crampy gas pains. You might also feel full quickly when eating (early satiety). While everyone experiences bloating occasionally (for example, after eating certain foods), persistent bloating or a constant full feeling that is new for you could be a sign of something more serious and warrants medical evaluation.
9. Pain or Discomfort During Bowel Movements
If you feel pain when trying to have a bowel movement or experience discomfort in the rectal area when sitting, it could be related to a growth in the rectum or lower colon. Colon cancer in the rectal area can make the act of passing stool painful. You might feel a sharp pain, pressure, or a burning sensation during the bowel movement. Some people also notice a change in how it feels to sit (due to a tumor in the rectum causing pressure). Any persistent rectal pain, especially if it’s a new sensation and not explained by an anal fissure or hemorrhoids, should be brought to a doctor’s attention. Pain with bowel movements combined with bleeding is particularly concerning.
10. Fatigue and Weakness
Feeling very tired, weak, or easily exhausted can be a generalized symptom of colon cancer, often due to chronic blood loss from the tumor. Colon cancers can bleed slowly over time, and you might not see the blood if it’s hidden in the stool. This bleeding can lead to iron deficiency anemia – a low red blood cell count – which reduces the oxygen-carrying capacity of your blood. The result is that you may feel constantly fatigued, weak, or short of breath with slight exertion. Unlike normal tiredness that improves with rest, cancer-related fatigue tends to be more persistent. If you find that you’re tired all the time, even after adequate sleep, or feel weak doing everyday activities, it could be a sign that something is wrong and should be evaluated with blood tests and further examination.
11. Unexplained Weight Loss
Losing weight without trying – for example, dropping pounds despite eating normally and not exercising more – can be a warning sign of colon cancer. Unintended weight loss is defined as losing 5% or more of your body weight within 6-12 months without a clear reason. In colon cancer, weight loss can occur due to the cancer using up energy, changes in metabolism, or loss of appetite from the tumor’s effects. If you notice your clothes fitting looser or see a significant decline on the scale without dieting, take note. Unexplained weight loss is a symptom that should prompt a medical checkup, as it can be associated with many types of cancer and other illnesses. In colon cancer, weight loss often occurs along with other symptoms like abdominal discomfort or altered bowel habits.
12. Loss of Appetite
A sudden or growing disinterest in eating, or feeling full quickly, can be another symptom of colon cancer. You might find that foods you used to enjoy no longer appeal to you, or you get satisfied after just a few bites. There are multiple reasons this can happen with cancer: the tumor can produce substances that affect appetite, or chronic illness can alter taste and hunger signals. Additionally, if the cancer causes nausea or discomfort, you may subconsciously eat less to avoid those feelings. Loss of appetite can contribute to the unexplained weight loss mentioned above. While many conditions can affect appetite (like stress or viral infections), a persistent drop in your desire to eat should be investigated. Maintaining nutrition is important, and any ongoing appetite loss warrants a discussion with a healthcare provider to find the cause.
13. Nausea and Vomiting
Colon cancer, especially when it grows large enough to partially block the intestine, can lead to nausea (a sick feeling in the stomach) and vomiting. You might feel queasy frequently or vomit without an obvious reason (such as a stomach bug). One scenario where vomiting occurs is if the bowel is obstructed by a tumor – food can’t pass through normally, causing a backup that triggers vomiting. In earlier stages, nausea might be mild and intermittent, but in later stages or with a bowel obstruction, it can be severe. If you experience recurring nausea or episodes of vomiting that don’t relate to a known cause (like food poisoning or pregnancy), it’s important to get evaluated. Nausea and vomiting can also accompany other colon cancer symptoms like abdominal pain and bloating, compounding the discomfort.
14. Jaundice (Yellowing of Skin and Eyes)
Jaundice is a yellowing of the skin and the whites of the eyes, and it typically indicates a liver issue. Colon cancer can cause jaundice if it spreads to the liver and impairs bile flow. When colon cancer metastasizes (spreads) to the liver, tumors there can block bile ducts or interfere with liver function, leading to a buildup of bilirubin in the body. The result is a yellow discoloration of the skin and eyes, often accompanied by dark urine and itchy skin. Jaundice is generally a sign of advanced colon cancer spread to the liver (or another serious liver condition). If you ever notice jaundice, it is critical to seek medical evaluation immediately. In the context of colon cancer, jaundice would usually appear in Stage IV disease (see Stages section below), and it might be one of the first signs that the cancer has metastasized to the liver.
15. Iron-Deficiency Anemia (Low Red Blood Cell Count)
Iron-deficiency anemia can be both a sign and a consequence of colon cancer. Many colon cancers bleed slowly into the colon. Over time, this blood loss means the body loses iron and can’t make enough healthy red blood cells. The anemia that results may be discovered on a routine blood test even before any obvious symptoms. In fact, sometimes the first clue to colon cancer is a blood test showing anemia. Symptoms of anemia include the fatigue and weakness mentioned above, as well as pale skin, dizziness, or shortness of breath on exertion. If you are found to have iron-deficiency anemia, especially if you are an older adult or a male (groups in which iron-deficiency anemia is less common without a clear cause), doctors will often investigate the gastrointestinal tract (including a colonoscopy) to look for sources of bleeding like colon cancer. Treating the cancer can often resolve the anemia over time.
Important: Having one or more of these symptoms does not mean you definitely have colon cancer – many of these signs overlap with benign conditions. However, if you experience any of these symptoms persistently (more than a couple of weeks) or if they worsen, you should see a healthcare provider. Early colon cancer might not cause any symptoms, so routine screening (such as colonoscopy) is recommended for adults over 45 or earlier if you have risk factors. The presence of symptoms often indicates that the cancer has grown larger or spread, which is why timely medical attention is so crucial.
Next, we’ll discuss how colon cancer is classified into stages, which describe how advanced the cancer is. Understanding the stages will also give insight into how symptoms tend to progress as the disease advances (for example, why later stages might produce more severe or additional symptoms like jaundice or significant pain).
Stages of Colon Cancer
After diagnosing colon cancer (typically via a biopsy during colonoscopy), doctors determine the stage of the cancer. The stage describes how much the cancer has grown and spread in the body. Staging is crucial because it guides treatment decisions and helps predict prognosis. In general, lower stage cancers are more localized and easier to treat, whereas higher stage cancers have spread further and may require more aggressive treatment.
Doctors most often use the AJCC TNM staging system for colon cancer. TNM stands for Tumor, Node, Metastasis, and it assesses three key factors about the cancer’s spread:
- T (Tumor) – How large the primary tumor is and how deeply it has grown into the layers of the colon. The colon wall has several layers, and tumor “T” status ranges from T1 (tumor in the inner layers) up to T4 (tumor has grown through the wall).
- N (Node) – Whether the cancer has spread to nearby lymph nodes (small immune glands next to the colon). N0 means no lymph nodes are involved, whereas N1 or N2 means the cancer is found in some nearby nodes.
- M (Metastasis) – Whether the cancer has spread to distant organs or distant lymph nodes in the body. M0 means no distant spread, and M1 means there is metastasis to organs like the liver, lungs, etc.
Using some combination of the T, N, and M categories, doctors assign an overall stage from 0 through IV (0, I, II, III, or IV). In colon cancer, there are five main stages (Stage 0 to Stage IV). Generally, Stage 0 is the very beginning (cancer in situ), Stage I is early disease, Stage II and Stage III are intermediate (with Stage III indicating lymph node involvement), and Stage IV is advanced metastatic cancer. Sometimes stages are further subdivided (like IIIA, IIIB, IIIC) based on specific criteria, but we will focus on the main stage groupings for clarity. Here’s an overview of each stage:
Stage 0 (Carcinoma in Situ)
Stage 0 colon cancer is the earliest stage, sometimes not even considered an invasive cancer yet. The cancer cells are found only in the innermost lining of the colon (mucosa) and have not grown any deeper. This stage is also called carcinoma in situ or intramucosal carcinoma. Often, Stage 0 cancers are discovered during routine screenings as polyps or tiny growths with cancerous cells on the surface. At this stage, the abnormal cells are localized to the colon’s lining and have not spread to lymph nodes or other organs (by definition, if they had, it would be a higher stage). Stage 0 is highly curable – usually treated by removing the polyp or the section of the lining containing the cancer cells. Patients at Stage 0 typically do not experience noticeable symptoms because the lesion is very small. This underscores the importance of screening: finding and removing a Stage 0 cancer can prevent it from growing into a more advanced (symptomatic) cancer.
Stage I (Early Invasive Colon Cancer)
In Stage I, the cancer has grown into the layers of the colon wall but is still confined to the colon and has not spread to lymph nodes or distant sites. Specifically, a Stage I colon cancer has invaded from the inner lining into the submucosa (the layer beneath the mucosa) and possibly into the muscular layer of the colon wall, but not beyond. You can imagine the colon wall like layers of an onion – Stage I means the cancer is in the inner layers but hasn’t penetrated all the way through. Because it hasn’t spread to lymph nodes (N0) or elsewhere (M0), Stage I is considered a localized cancer. Many Stage I colon cancers still might not cause obvious symptoms; however, some patients at this stage do experience some of the earlier-mentioned symptoms like changes in bowel habits or slight bleeding. Often, Stage I cancers are found during colonoscopies done for other reasons or screening. Treatment for Stage I is typically surgical removal of the tumor and a portion of surrounding normal colon. The prognosis at this stage is usually very good, with high survival rates, because the cancer is still limited in extent.
Stage II (Locally Advanced Colon Cancer)
Stage II colon cancer means the tumor has grown through or beyond the muscular layer of the colon wall, and possibly into nearby tissues, but still has not spread to any lymph nodes (N0) and has not metastasized to distant organs (M0). In simpler terms, Stage II is characterized by a larger or deeper tumor in the colon. Stage II is often subdivided:
- Stage IIA: The cancer has grown through the muscle layer to the outermost layer of the colon (the serosa).
- Stage IIB: The cancer has grown through the serosa (outer layer) of the colon wall, but has not invaded nearby organs.
- Stage IIC: The cancer has grown through the colon wall and is touching or invading nearby organs or structures, but still no lymph node involvement.
Despite the tumor’s size or depth in Stage II, the key factor is that it has not reached the lymph nodes. Symptoms in Stage II can start becoming more pronounced compared to Stage I. A tumor that has grown larger may cause more noticeable changes in bowel habits, more frequent abdominal pain, or more obvious blood in the stool. For example, a Stage II tumor that fully penetrates the colon wall might cause localized peritoneal irritation (leading to pain) or even be felt by a doctor during a physical exam if it’s large enough. However, some Stage II cancers still might not produce severe symptoms, and they might be discovered during surgery or imaging for something else. Treatment for Stage II typically involves surgery to remove the affected section of colon and nearby lymph nodes (even though lymph nodes are not yet positive for cancer, they are removed as a precaution and for accurate staging). Depending on specific features (like if the tumor looks aggressive under the microscope), chemotherapy might be recommended after surgery in some Stage II cases. The prognosis is still quite good, especially for Stage IIA, while Stage IIC (which involves other organs) can be more complex to treat.
Stage III (Regionally Advanced Colon Cancer)
Stage III colon cancer is characterized by spread to nearby lymph nodes. In Stage III, the tumor can be of any size or depth (it may still be just within the colon wall or may have grown through it), but importantly, cancer cells have been found in regional lymph nodes (N1 or N2 status). There is no distant metastasis in Stage III (M0 – if there were, it would be Stage IV). Like Stage II, Stage III is often divided into subcategories (IIIA, IIIB, IIIC) based on how extensive the tumor is in the colon wall and how many lymph nodes are involved:
- Stage IIIA: Cancer is in the inner layers of the colon wall (much like Stage I) and 1-3 lymph nodes have cancer, or it has spread into nearby fat tissue near nodes (N1/N1c).
- Stage IIIB: Cancer has grown deeper into the colon wall (into or through the outer layers) and has spread to 1-3 lymph nodes, or it’s a slightly less deep tumor but with 4-6 lymph nodes involved.
- Stage IIIC: A more advanced local tumor (through the wall, possibly into other organs) and cancer in 4 or more lymph nodes.
In all cases, Stage III indicates a regional spread to lymph nodes, which means the cancer cells have traveled to the first draining sites of the colon. This stage is significant because once lymph nodes are involved, there’s a higher chance that cancer cells could travel further through the lymphatic or blood system. Symptoms in Stage III might be similar to Stage II but often more pronounced. There may be more bleeding (potentially leading to anemia and severe fatigue), more persistent abdominal pain or cramps, and possibly weight loss and weakness. Sometimes, if many lymph nodes are involved, it implies the tumor has been growing for longer, which could correlate with larger tumor size or ulceration (which can cause infections or more pain). Treatment for Stage III usually involves surgery to remove the tumor and affected lymph nodes followed by chemotherapy. Chemotherapy is standard in Stage III colon cancer because it helps destroy any cancer cells that have spread to lymph nodes and reduce the risk of the cancer coming back. The prognosis for Stage III varies by the extent of node involvement – cancers with only a few nodes involved (IIIA/IIIB) have better outcomes than those with many nodes (IIIC) – but with modern treatments, many Stage III patients are cured.
Stage IV (Metastatic Colon Cancer)
Stage IV colon cancer is the most advanced stage, in which the cancer has spread to distant parts of the body beyond the colon and nearby nodes. This is also known as metastatic colon cancer. Common sites for colon cancer metastases are the liver and lungs, but it can also spread to distant lymph nodes, the lining of the abdominal cavity (peritoneum), or other organs like the ovaries (in women). In Stage IV, the primary tumor in the colon can be of any size, and lymph nodes may or may not have cancer – the defining feature is distant spread (M1). Stage IV is often classified further based on how widespread the metastasis is:
- Stage IVA: The cancer has spread to one distant organ or site (for example, the liver only) or to a distant set of lymph nodes.
- Stage IVB: The cancer has spread to multiple distant sites (e.g., liver and lung).
- Stage IVC: Cancer has spread to distant sites and also the peritoneum (abdominal lining) or has an extensive spread to multiple organs.
At Stage IV, patients often experience more severe symptoms. In addition to any combination of the local symptoms (bowel changes, bleeding, pain), there may be systemic symptoms such as significant weight loss, loss of appetite, and fatigue. Symptoms related to the specific metastatic sites also appear. For instance, if the cancer has spread to the liver, one might develop jaundice or abdominal swelling; if it has spread to the lungs, one might experience a chronic cough or difficulty breathing; if the peritoneum is involved, it can cause ascites (fluid buildup in the abdomen, leading to distension and discomfort). The presence of metastases often means the cancer has been growing unchecked for some time. Treatment for Stage IV colon cancer can be more complex and typically involves a combination of therapies. Surgery might be done to remove the colon tumor if possible (especially if it’s causing obstruction or bleeding). If there are only a few metastases (for example, a couple of tumors in the liver or lungs), those might sometimes be surgically removed or treated with methods like ablation. Chemotherapy is a mainstay for Stage IV, often combined with targeted therapy drugs that specifically attack cancer cell markers. Immunotherapy may be an option for certain patients (especially if the tumor has specific genetic features like MSI-H/dMMR status). The goal of treatment might be to control the cancer and extend life, and in some cases of limited metastasis, long-term remission or cure is possible. Even when a cure isn’t likely, treatment can often help shrink tumors, relieve symptoms, and improve quality of life.
How Stages Are Determined: Determining the stage of colon cancer usually involves a combination of imaging tests and surgical pathology. Before surgery, doctors use imaging studies like CT scans, MRIs, or PET scans to look for any spread to lymph nodes or organs. A chest scan checks the lungs, and an abdominal scan checks the liver and other organs for metastases. During surgery for colon cancer, the surgeon removes the tumor along with nearby lymph nodes. A pathologist then examines the tissue under a microscope to see how deep the tumor went (T stage) and how many lymph nodes have cancer (N stage). The presence of any cancer in organs like the liver or in distant lymph nodes would indicate metastasis (M stage). By combining this information, the medical team assigns the final stage. For example, a tumor that has grown through the colon wall, with 2 positive lymph nodes and no distant spread, would be T3 N1 M0, which corresponds to Stage III. In contrast, a small tumor confined to the inner layer but with a small metastasis in the liver would be T1 N0 M1, which is Stage IV because of the metastasis. Staging might be updated after surgery (called pathologic staging) if it provides more information than initial clinical staging.
Symptom Progression and Staging: It’s important to connect how the stages relate to symptoms. Early-stage colon cancers (Stage I and II) are often silent or cause only mild symptoms (if any). You might have a bit of constipation or a little blood on the stool occasionally and not think much of it. By Stage III, the chances of noticeable symptoms increase – the tumor is larger and lymph node involvement suggests the cancer has been growing longer, so issues like persistent bowel habit changes, more frequent bleeding, and fatigue from anemia are more common. By Stage IV, the cancer’s impact is often widespread: in addition to the primary tumor’s effects (which could be severe by now), the metastatic tumors cause new problems (for example, liver metastasis causing jaundice or abdominal pain, lung metastasis causing coughing or breathlessness). In summary, as the stage advances, symptoms tend to become more pronounced and multifaceted. This is why catching colon cancer early (through symptom awareness and routine screening) is so critical – early-stage colon cancer is much easier to treat and has a higher cure rate, while late-stage colon cancer is more challenging and can affect many aspects of health.
Conclusion
Colon cancer can present with a variety of symptoms – some are subtle changes like mild changes in bowel habits, and others are more glaring like blood in the stool or significant abdominal pain. Recognizing these 15 symptoms and understanding that persistent, unexplained gastrointestinal issues warrant medical attention can lead to earlier detection of colon cancer. Equally important is understanding the staging system: it provides a framework for how advanced the cancer is, what kind of treatments may be needed, and what kind of outcomes to expect. Early-stage (Stage I) colon cancers confined to the colon wall have an excellent prognosis, whereas Stage IV cancers that have spread to other organs are serious and require comprehensive treatment.
If you or someone you know is experiencing symptoms like those described above, do not panic – many of these signs can be caused by conditions other than cancer. However, do get them checked by a healthcare provider, especially if you have risk factors for colon cancer (such as being over age 50, a family history of colorectal cancer, or a history of inflammatory bowel disease). Doctors may perform tests like a colonoscopy, blood tests (for anemia or tumor markers), and imaging scans to determine the cause of the symptoms. For those diagnosed with colon cancer, knowing the stage helps in understanding the journey ahead. With modern treatments – surgery, chemotherapy, radiation (more often used in rectal cancer), targeted therapies, and immunotherapy – many patients with colon cancer can be treated effectively, and survival rates have been improving.
Finally, keep in mind the importance of preventive measures: screening colonoscopies can remove precancerous polyps and detect cancer early (often before symptoms develop), and lifestyle changes such as a healthy diet, regular exercise, not smoking, and moderating alcohol can lower your risk of colon cancer. Awareness of symptoms and proactive healthcare can truly make a life-saving difference when it comes to colon cancer.
Sources
- Mayo Clinic – Colon Cancer Symptoms
https://www.mayoclinic.org/diseases-conditions/colon-cancer/symptoms-causes/syc-20353669 - American Cancer Society – Signs and Symptoms of Colorectal Cancer
https://www.cancer.org/cancer/colon-rectal-cancer/detection-diagnosis-staging/signs-and-symptoms.html - American Cancer Society – Colon Cancer Staging (TNM Staging for Colon Cancer)
https://www.cancer.org/cancer/colon-rectal-cancer/detection-diagnosis-staging/staging.html - National Cancer Institute – Colorectal Cancer Overview
https://www.cancer.gov/types/colorectal - CDC – Colorectal Cancer Basic Information (Symptoms)
https://www.cdc.gov/cancer/colorectal/basic_info/symptoms.htm - National Cancer Institute PDQ – Colon Cancer Treatment
https://www.cancer.gov/types/colorectal/hp/colon-treatment-pdq - Mayo Clinic – Colon Cancer Diagnosis and Treatment (including Imaging)
https://www.mayoclinic.org/diseases-conditions/colon-cancer/diagnosis-treatment/drc-20353670 - American Cancer Society – Key Statistics for Colorectal Cancer
https://www.cancer.org/cancer/colon-rectal-cancer/about/key-statistics.html
This article is intended for educational purposes. For personalized medical advice, always consult a healthcare professional.
