The short answer: A colon tattoo is a small injection of sterile ink, placed so a surgeon or endoscopist can find the same spot again. The 2020 US Multi-Society Task Force guidance recommends sterile carbon ink for marking colon lesions that doctors need to find again. A tattoo marks a location. It is not a diagnosis of cancer.
What exactly did my doctor inject?
During the colonoscopy, your doctor used a thin needle passed through the scope to inject a dark ink into the inner layer of the colon wall. The ink leaves a blue-black stain that can be seen from inside the bowel with a scope, and often from outside the bowel during surgery.
The most common ink in the United States is a sterile carbon particle suspension. The best-known brand, Spot, was cleared by the FDA in February 2000 through the 510(k) pathway as a colon marker (product code NBG). The 2020 US Multi-Society Task Force guidance on endoscopic removal of colorectal lesions specifically recommends sterile carbon particle suspension as the tattoo agent. Older practice used diluted India ink, and some hospitals still do.
You did not feel the injection. The inner lining of the colon does not sense a needle the way skin does, and you were most likely sedated.
Why would a doctor tattoo a polyp or lesion?
The inside of the colon looks much the same along its length. Once the scope is out, it can be hard to say exactly where a spot was. A tattoo solves that problem. Common reasons include:
- Planned surgery. In keyhole (laparoscopic) surgery, the surgeon cannot feel the bowel with their hands. A small tumor may be invisible from the outside. The tattoo shows them which segment to remove.
- A polyp left in place. If a polyp is large or flat, your doctor may stop and refer you to a specialist for removal. An international Delphi consensus of 29 experts (2021) agreed tattooing may be used when that lesion would be hard to find at the next scope.
- A polyp that was removed but looked worrisome. The same consensus reached its highest agreement on one point: a tattoo should always be placed after removing a lesion suspected of invading deeper (the submucosa). If the lab confirms cancer, the surgeon needs to find the scar.
- Checking the site later. After a large polyp is removed in pieces, a follow-up scope looks for leftover tissue. The tattoo points to the right area.
Tattoos help surgery go as planned. In a 2023 Irish study of 169 laparoscopic resections, the 11 patients whose tumors had no useful tattoo had a 55% conversion rate to open surgery, compared with 23% overall.
Does a tattoo mean I have cancer?
No, not by itself. A tattoo tells you your doctor wanted to be able to find a spot again. It does not tell you what that spot is. Tattoos are often placed on large benign polyps (adenomas) referred for specialist removal, and on lesions that looked suspicious but prove noncancerous.
That said, a tattoo does mean your doctor saw something worth tracking. In the Irish study above, 54% of tattooed lesions that went to surgery were malignant, so 46% were not. That figure comes from a surgical group, so it describes people who already needed an operation, not everyone with a tattoo.
The real answer is in your pathology report. If a biopsy or polyp was sent to the lab, see how long colonoscopy biopsy results take. Waiting can be hard. If worry is affecting your sleep or work, anxiety.md covers practical ways to manage health anxiety.
Where is the tattoo placed?
The tattoo usually goes next to the lesion, not into it. The 2020 Task Force guidance suggests placing the tattoo at 2 to 3 separate sites, 3 to 5 cm on the anal side (downstream) of the lesion. It also recommends that endoscopists and surgeons agree on a standard location, and that the report document the tattoo details.
There is a reason the ink stays away from the polyp. Carbon ink under a lesion can cause scarring (fibrosis), which makes later removal through the scope harder. The Task Force recommends against using the tattoo ink as the lifting fluid, and the Delphi panel agreed a tattoo should never be injected directly into or under a lesion that might be removed endoscopically later.
In practice, placement varies. A Canadian review of 1,062 colorectal resections found the tattoo location relative to the lesion was not documented in 67% of tattooed cases. If your report just says "tattooed," you can ask where.
Is a colon tattoo permanent?
Usually, yes. Carbon particles stay in the bowel wall for years. A 1997 study of 55 patients biopsied India ink tattoos placed up to 117 months (almost 10 years) earlier. The tattoos were still visible at surveillance colonoscopy. There were no infections, fevers, or abdominal pain, and no cancerous changes in the tissue over the tattoos.
You will not see the tattoo on your skin, and it does not affect daily life. If the tattooed segment is removed in surgery, the ink leaves with it.
Is colon tattooing safe?
It is generally safe. In a series of 50 patients tattooed before laparoscopic surgery, no complications related to the endoscopy or tattooing occurred. Problems are reported mainly as individual case reports.
The main known risk is ink passing all the way through the bowel wall into the abdomen. This can cause local inflammation and, rarely, peritonitis. A 2025 case report described a man whose staging CT showed a small perforation after tattooing. He had no symptoms and recovered with supportive care alone.
Tattoos are also not foolproof. In a Cleveland Clinic Florida study of 203 colon resections, 3.8% of tattooed lesions could not be identified during surgery. Call your doctor for severe belly pain, fever, or heavy bleeding in the days after any colonoscopy. See blood in stool after polyp removal for what is normal.
What happens after your report says "tattooed"?
These steps follow the pathway in the cited guidance and studies. Your own plan depends on what was found.
- Read the full report. Look for the lesion size, location, whether it was removed, and where the tattoo sits (for example, "3 cm distal"). The Task Force recommends this detail be documented.
- Wait for pathology. If tissue was removed or sampled, the lab result decides the next step. Ask when and how you will get it.
- If the polyp was benign and fully removed, you usually return for surveillance. The tattoo helps the next doctor check the site. See colonoscopy intervals after polyps.
- If the polyp was left in place, expect a referral for specialist endoscopic removal. Bring your report, since the tattoo marks the target.
- If cancer is confirmed or suspected, expect staging scans and a surgical consult. The surgeon uses the tattoo to find the right segment.
- At any later colonoscopy, tell the new doctor you have a tattoo and where it is.
The bottom line
A colon tattoo is a map marker. Your doctor placed it so that a surgeon or the next endoscopist can find the same spot. It does not mean you have cancer, and it usually lasts for years without causing problems. Your pathology report and your doctor's follow-up plan tell you what the marked spot actually is. For background on polyp types, see colon polyps explained.
Last updated: October 2026. This article is for informational purposes only and does not constitute medical advice. Talk with your gastroenterologist about what your colonoscopy report and pathology results mean for you.