Hemorrhoids do not cause cancer. No biological mechanism has been identified by which swollen anal or rectal veins transform into malignant tissue, and the largest studies directly examining the question find no causal link. What hemorrhoids can do, however, is mask the symptoms of a cancer that is already developing nearby, and that masking effect is a genuinely serious clinical problem. The overlap in symptoms between hemorrhoids and colorectal or anal cancer is so strong that it delays diagnosis for thousands of people every year.
Why the Confusion Exists
Hemorrhoids and colorectal cancer share a short list of symptoms that are hard to tell apart without investigation. Both can cause rectal bleeding, a sense of fullness or pressure in the rectum, changes in bowel habits, and discomfort during bowel movements. Because hemorrhoids are extraordinarily common and cancer is relatively rare, most people who notice blood on toilet paper or in the bowl reasonably assume hemorrhoids are to blame. And most of the time, they are right.
But “most of the time” is not all of the time. One study of patients referred for rectal bleeding found that even among those with classic hemorrhoid-type bleeding (bright red blood not mixed with stool), about 2% had a colorectal cancer present at the same time.1PubMed Central. Predicting colorectal cancer risk in patients with rectal bleeding That number is small in percentage terms, but rectal bleeding is so common that 2% adds up to a lot of missed cancers across the population.
How Symptoms Differ Between Hemorrhoids and Cancer
There are differences between hemorrhoid symptoms and cancer symptoms, though they are not always clear-cut in an individual case. Hemorrhoid bleeding tends to be bright red, appears on the surface of stool or on toilet paper, and often comes and goes depending on straining, diet, or activity level. Cancer-related bleeding is more likely to be persistent and may produce darker blood, sometimes mixed into the stool itself rather than coating its surface.2Moffitt Cancer Center. How to Tell the Difference Between Hemorrhoids and Colon Cancer
A systematic review looking at the clinical overlap between hemorrhoids and rectal cancer identified several warning signs that point toward cancer rather than hemorrhoids:
- Dark red blood: Blood that is darker than the typical bright red of hemorrhoid bleeding, especially when it appears mixed with stool.
- Persistent anorectal pain: Hemorrhoids can hurt, particularly thrombosed external hemorrhoids, but pain that does not resolve or worsens over weeks deserves further investigation.
- Unexplained weight loss: This is not a hemorrhoid symptom. Losing weight without trying alongside any rectal symptoms is a red flag that warrants prompt medical evaluation.
These warning signs were identified as features more suggestive of rectal cancer than hemorrhoids.3PubMed Central. Hemorrhoids and Rectal Cancer: A Systematic Review of Clinical Overlap, Diagnostic Misclassification, and Early Detection Strategies for Primary Care Other symptoms that should prompt further workup include a new, sustained change in the caliber or frequency of stools, a feeling that the bowel does not fully empty, and iron-deficiency anemia (which can develop from slow, chronic blood loss that you might not even see).
The Real Danger: Hemorrhoids as a Diagnostic Mask
If hemorrhoids do not cause cancer, why does research keep linking the two? Because hemorrhoids are the single most common wrong answer when a cancer is the real problem. In a study of patients whose colorectal cancer diagnosis was delayed by a missed diagnostic opportunity, hemorrhoids were the most frequent alternate diagnosis given. Patients who received a wrong initial diagnosis, including hemorrhoids, waited an average of about 9 months before their cancer was correctly identified, compared to 2 months for patients without a misdiagnosis.4PubMed Central. Missed Opportunities for the Diagnosis of Colorectal Cancer That seven-month gap is not trivial. In that time, a cancer can progress from a stage where treatment is straightforward to one where it is much harder.
The problem is not limited to doctors making mistakes. Patients themselves contribute to the delay. Research on people eventually diagnosed with rectal cancer found that more than half initially attributed their symptoms to hemorrhoids, and over three-quarters did not believe their symptoms were caused by anything serious.5PubMed Central. Delayed treatment for rectal cancer Qualitative research among colorectal cancer patients in Thailand echoed this: patients described being unaware of colorectal cancer as a possibility and considered their symptoms to be hemorrhoids.6PubMed. “Just Hemorrhoids, Not Cancer”: Perceptions of Colorectal Cancer Among Thai Colorectal Cancer Patients
This combination of patient self-reassurance and occasional clinical misjudgment creates a diagnostic trap. A person with rectal bleeding sees their doctor, gets told they have hemorrhoids (often correctly, since hemorrhoids are present in roughly half of adults by middle age), receives treatment, and stops worrying. If they also happen to have an early cancer, it may grow undetected for months.
Hemorrhoids and Cancer Coexisting
Hemorrhoids and colorectal cancer are not mutually exclusive. Having hemorrhoids does not protect you from cancer, and having cancer does not mean you cannot also have hemorrhoids. A colonoscopy study of patients with rectal bleeding found that roughly 30% had clinically significant findings including adenocarcinomas and adenomatous polyps. Among those, some patients had hemorrhoids simultaneously, with two patients found to have both hemorrhoids and a cancer or polyp located further up in the colon.7PubMed Central. Colonoscopic evaluation of minimal rectal bleeding in average-risk patients for colorectal cancer
An endoscopy-based study of over 6,000 patients found that among those who had hemorrhoids, roughly 1 in 22 also had a malignancy present.8Thieme Connect / Ibnosina Journal of Medicine and Biomedical Sciences. Exploring the Association between Benign Anorectal Conditions and Colorectal Cancer from the Analysis of Lower Gastrointestinal Endoscopies That does not mean hemorrhoids caused the malignancy. It means the two conditions were found in the same person during the same exam, which reinforces why stopping at a hemorrhoid diagnosis without looking further can be risky.
A Taiwanese Cohort Study and the Question of Surveillance Bias
One large population-based study has been widely cited in discussions about hemorrhoids and cancer risk. This retrospective cohort study, using Taiwan’s national health insurance database, followed patients with hemorrhoids over roughly a decade and found that the overall rate of colorectal cancer was about 2.4 times higher in hemorrhoid patients than in a comparison group. After adjusting for age, sex, and other health conditions, the hazard ratio was 2.18.9PubMed Central. Colorectal Cancer Risk in Patients with Hemorrhoids: A 10-Year Population-Based Retrospective Cohort Study That looks alarming at first glance, but the study’s authors and other researchers have pointed to an important caveat: people who see a doctor for hemorrhoids are more likely to undergo colonoscopy and other investigations, meaning cancers in that group are more likely to be found. This is a textbook example of surveillance bias, where the act of being in the medical system increases the chance of detecting something.
The same study also reported that hemorrhoid surgery appeared to cut subsequent colorectal cancer incidence by about half.9PubMed Central. Colorectal Cancer Risk in Patients with Hemorrhoids: A 10-Year Population-Based Retrospective Cohort Study Again, the most plausible explanation is not that removing hemorrhoids prevents cancer. It is that surgical patients undergo thorough pre-operative and post-operative examinations, during which any coexisting polyps or early cancers get caught and treated. The surgery itself involves careful visual inspection of the anorectal area, and patients undergoing hemorrhoid procedures are typically screened more aggressively than the general population. In other words, the finding may say more about the power of medical surveillance than about any biological relationship between hemorrhoids and malignancy.
Do Hemorrhoids Increase Anal Cancer Risk?
Anal cancer is a different disease from colorectal cancer, driven primarily by human papillomavirus (HPV) infection rather than the polyp-to-cancer sequence seen in the colon. The question of whether hemorrhoids or other benign anal conditions promote anal cancer has been investigated directly.
A study published in the British Journal of Cancer examined whether benign anal lesions, including hemorrhoids, fissures, and fistulas, played a role in anal cancer development. It found that risk associations with benign anal lesions in men could be confounded by unreported sexual behavior (a known HPV transmission route), and that in women the associations were generally negative. The researchers concluded that benign anal lesions are unlikely to act as promoters in HPV-associated anal cancer and do not appear to be linked to an alternative causal pathway to anal cancer independent of HPV.10British Journal of Cancer. Benign anal lesions, inflammatory bowel disease and risk for high-risk human papillomavirus-positive and -negative anal carcinoma
A large Danish cohort study reinforced this. While inflammatory anal conditions like fissures and fistulas showed some elevated anal cancer risk, hemorrhoids specifically did not. The researchers noted that inflammatory lesions may facilitate HPV access to the epithelium or act as a cofactor in HPV-related cancer development, but that noninflammatory benign lesions like hemorrhoids did not carry the same elevated risk.11Cancer Epidemiology, Biomarkers & Prevention. Risk of Anal Cancer Following Benign Anal Disease and Anal Cancer Precursor Lesions: A Danish Nationwide Cohort Study
When Rare Cancers Hide Behind Hemorrhoid Symptoms
Anal cancer itself is uncommon, accounting for only about 1 to 2 percent of all large bowel cancers. But when it does occur, it is frequently misdiagnosed as hemorrhoids. One review of 50 anal cancer patients at two institutions found that the most common type was squamous cell carcinoma (88% of cases), with smaller numbers of melanoma, adenocarcinoma, and Paget’s disease. By the time of diagnosis, over 70% had stage II disease or higher.12The American Surgeon. Anal Carcinoma or “Just Hemorrhoids”?
Anorectal melanoma is an especially tricky mimic. It is exceedingly rare but aggressive, and its presenting symptoms (a mass near the anus, bleeding, discomfort) look clinically identical to hemorrhoids. Case reports describe patients treated for hemorrhoids for extended periods before the melanoma was identified.13PubMed Central. Anorectal Melanoma: An Unusual Cause of Rectal Bleeding The rarity of these cancers makes them hard to diagnose precisely because clinicians are not expecting them, and the default assumption when examining the anorectal area is almost always hemorrhoids.
What Current Clinical Guidelines Recommend
The American Society of Colon and Rectal Surgeons acknowledges the diagnostic overlap and has built safeguards into its hemorrhoid management guidelines. A colonoscopy is recommended when no obvious source of bleeding is found on initial exam, when the patient has associated abdominal symptoms like pain, bloating, or new or worsening constipation, and when the patient is due for routine colorectal cancer screening. Patients who continue to bleed after successful hemorrhoid treatment should also undergo further investigation.14Diseases of the Colon & Rectum. The American Society of Colon and Rectal Surgeons Clinical Practice Guidelines for the Management of Hemorrhoids
That last point deserves emphasis. If your hemorrhoids have been treated and the bleeding stops, that is reassuring. If the bleeding continues or recurs after treatment, the working diagnosis needs to be reconsidered. Persistent bleeding after adequate hemorrhoid treatment is one of the clearest signals that something else may be going on.
Practical Guidance for People With Hemorrhoids
If you have hemorrhoids and are worried about cancer, here is what the evidence actually suggests you do:
- Stay current on screening: Standard colorectal cancer screening (typically starting at age 45 in the United States) catches polyps and early cancers before symptoms ever appear. If you have hemorrhoids, you are not at higher cancer risk, but you are at higher risk of dismissing symptoms that could matter.
- Track your symptoms: If rectal bleeding changes in character (darker, more persistent, mixed into stool), or if you develop new symptoms like unexplained weight loss, persistent abdominal pain, or a sustained change in bowel habits, see a doctor even if you think it is “just your hemorrhoids.”
- Do not self-diagnose forever: Many people manage hemorrhoids at home with over-the-counter treatments for years without ever getting a formal evaluation. That approach probably works for most people, but it means there is never a clinical exam that could catch something else.
- Report persistent bleeding after treatment: As the surgical guidelines note, bleeding that continues after hemorrhoids have been successfully treated is a reason for further investigation, not reassurance.
Why the “Hemorrhoids Cause Cancer” Myth Persists
Several factors keep this misconception alive. The symptom overlap is genuine and confusing. The Taiwanese cohort study, with its headline finding of doubled cancer risk, gets cited in health media without sufficient context about surveillance bias. And the lived experience of people who were diagnosed with cancer after being told they had hemorrhoids creates powerful anecdotal associations. When someone tells you their father was misdiagnosed with hemorrhoids and turned out to have colon cancer, it is natural to conclude that hemorrhoids led to cancer. In reality, the hemorrhoid diagnosis was wrong from the start, or both conditions were present simultaneously.
The distinction matters because treating hemorrhoids as a cancer risk factor could lead to unnecessary anxiety and over-investigation in the millions of people who have them, while the real lesson is simpler: do not let any diagnosis, hemorrhoids included, become a reason to stop paying attention to your body. Hemorrhoids are overwhelmingly benign, but they sit in the same anatomical neighborhood as cancers that kill people when found late. The fix is not to fear hemorrhoids. It is to take rectal bleeding seriously enough to get it properly evaluated, especially if it does not fit the typical hemorrhoid pattern or does not resolve with treatment.