What is Tubular Adenoma?
Colonic adenomas are raised growths, or polyps, on the inside lining of the colon that are made of glandular tissue. Even though they are benign or non-cancerous growths, they are often seen as precancerous because they can change into cancerous structures. This is not the same as hyperplastic polyps, which do not have the potential to turn cancerous.
These adenomas, or tumors, can differ in their growth pattern. They can be villous, tubular, or a mix of both referred to as tubulovillous. A polyp with predominantly villous features, meaning more than 75% of it has long, finger-like or leaf-like projections on its surface, is called a villous adenoma. In contrast, tubular adenomas are mainly made of tubular glands and have less than 25% villous features. When an adenoma has both features, it’s referred to as a tubulovillous adenoma. The most common type of colonic adenomas are tubular adenomas, making up over 80% of cases.
Even though villous adenomas are more frequently found to become cancerous, this is usually because they have a larger surface area due to the finger-like projections. However, when you consider their surface area, all types of adenomas have the same chance of turning cancerous.
What Causes Tubular Adenoma?
According to data gathered in local communities, the chance of getting colon cancer goes up with age and is more common in men. There are also multiple studies that indicate a higher risk among individuals who have a close family member with a history of colon cancer, people who smoke, consume too much alcohol, have diabetes, or are heavy for their height. This last group can be reflecting unhealthy lifestyle choices such as a diet high in fat with not much fiber and not enough physical activity.
In the past, researchers have found that black individuals were more likely to develop colonic adenoma and colon cancer than white individuals. However, recent studies have shown conflicting results. On a broader scale, more people in developing countries appear to have this disease than in North America, Australia, or Europe. However, there’s an increasing trend globally in cases of colon cancer, likely due to the adoption of Western dietary habits and lifestyles.
Risk Factors and Frequency for Tubular Adenoma
Colorectal cancer is one of the most common cancers and is the second biggest cause of cancer-related deaths in the United States, making it a major public health issue. One method used to estimate the risk of developing colorectal cancer is through adenoma detection rate (ADR). This rate tells us what percentage of people aged 50 and above, who are having a colonoscopy for cancer screening for the first time, had at least one adenoma found. By the time people reach their 50s, the ADR is typically around 12%, and over their lifetime it can increase to 50%. ADR can vary widely among different groups, reaching up to 22% in some large screenings. ADR is an important risk estimation tool, and interestingly, the higher the ADR, the lower the cancer risk. For instance, a 1% increase in ADR means a 3% decrease in cancer risk.
Signs and Symptoms of Tubular Adenoma
Adenomas, which are types of growths, are mainly found in the rectosigmoid area of the colon, but sometimes they appear in the upper part of the colon too. Most people with adenomas don’t show any symptoms which is why these growths are typically discovered during routine colonoscopies. However, if symptoms do occur, the most common one is hematochezia, which is bleeding from the rectum. This bleeding can be painless and may appear as bright or dark red blood during bowel movements, either mixed with stool or dripping.
Sometimes, people with adenomas can experience changes in their bowel movements such as diarrhea or constipation, weight loss, loss of appetite, or stomach pain. They could also show signs of a partial blockage in the intestine or develop iron deficiency anemia due to consistent bleeding. A physical examination won’t usually reveal any problems, but in rare cases, doctors may find rectal polyps during a digital rectal exam.
Symptoms of adenomas may include:
- Rectal bleeding (hematochezia)
- Changes in bowel movements, such as diarrhea or constipation
- Weight loss
- Loss of appetite
- Abdominal pain
- Symptoms of partial bowel blockage
- Iron deficiency anemia due to bleeding
Testing for Tubular Adenoma
According to the latest guidelines issued by the U.S. Preventive Services Task Force, it’s advisable to start screening for colorectal cancer at the age of 50 and continue until 75 years of age. For people aged between 76 and 85, the decision to proceed with screening should be adjusted based on their overall health and history of previous screenings.
Screening for growths in the colon, known as polyps, is usually done by testing for hidden or ‘occult’ blood in the stool, and via a procedure known as a colonoscopy, which is considered the gold standard. Most of the time, polyps don’t exhibit any symptoms, but they can sometimes lead to bleeding. A variety of methods can pick up these polyps, which include stool blood tests, digital rectal exams, flexible sigmoidoscopy, colonoscopy, virtual colonoscopy, barium enema, or a pill camera. To confirm the type of growth definitively, a colonoscopy is necessary, followed by a pathological examination.
Besides just initial screening, persistent monitoring via colonoscopy should continue if polyps have been found before. If the first colonoscopy doesn’t reveal any polyps, it’s generally recommended that the next check-up happens in about ten years. Follow-up for previously found polyps is typically conducted with a colonoscopy in three to five years, depending on the size of the removed polyp, and the presence of specific microscopic features known as ‘dysplastic features’. If more than ten growths or an adenoma exhibiting specific features is found, screening should occur in less than three years. For cases with 3 to 10 growths, screening should be conducted in 3 years. And if only 1 or 2 small growths are discovered, the screening interval may be extended for 5 to 10 years.
Regrettably, despite these surveillance guidelines, recent studies indicate that adherence to follow-up screenings is low. It’s crucial to take measures to boost these numbers. During a colonoscopy, up to 25% of polyps, particularly flat lesions on the right side of the colon, can go unnoticed due to poorly prepared intestines and challenges envisaging behind the mucosal folds lining the intestine. Current research is focusing on improving detection rates by leveraging accessory diagnostic devices and enhancing endoscope design.
Treatment Options for Tubular Adenoma
The main goal is to remove a type of abnormal tissue growths in the colon known as adenomatous polyps, before they potentially develop into a type of colon cancer called adenocarcinoma. It is challenging to tell the difference between hyperplastic (non-cancerous) and adenomatous (potentially cancerous) polyps just by looking at them. That’s why doctors usually remove all polyps found during a colonoscopy so that they can be examined under a microscope. In some severe cases, if there’s evidence of cancer or cancer spread to lymph nodes, the complete removal of the colon, known as a total colectomy, may be necessary.
Pseudopolyps, which have a moderate risk of developing into cancer, might cause bleeding or blockade in the colon. The best treatment approach for pseudopolyps is still subject to debate, even though various medical and surgical options are available.
In case of a condition called familial juvenile polyposis, the treatment approach is usually surgical and is chosen based on how much the rectum is affected. If there are fewer polyps in the rectum, a procedure called total abdominal colectomy with ileorectal anastomosis (removing the colon and attaching the small intestine to the rectum) could be performed, with regular check-ups for the part of rectum left behind. But if the rectum is densely populated with polyps, a total proctocolectomy (removal of both the colon and rectum) would be more appropriate. In such cases, ileal pouch-anal reconstruction can be done to avoid a permanent opening for waste removal, called a stoma.
There are three primary surgical approaches for treating a condition called familial adenomatous polyposis. These include the total removal of the colon and attaching the small intestine to the rectum, the complete removal of both the colon and rectum with the creation of a stoma, and a restorative proctocolectomy where the colon and rectum are removed but a pouch made from the intestine is attached to the anus, with or without the removal of the inner lining of the rectum.
What else can Tubular Adenoma be?
There are various types of polyps (abnormal tissue growths) and syndromes involving polyps, disorders that present differing risks and symptoms. Here’s a condensed, easy-to-understand version of them:
- Inflammatory polyps (pseudopolyps): Commonly connected to inflammatory bowel diseases, they can also be caused by other infections and conditions such as amoebic, ischemic, and schistosomal colitis. Pseudopolyps bigger than 1.5 cm are classified as giant pseudopolyps and may indicate a significant disease.
- Familial juvenile polyposis: A hereditary condition where abnormal growths mostly appear in the colon and rectum. These polyps can possibly turn malignant, so yearly screenings are recommended starting from age 10-12.
- Hyperplastic polyps: Most commonly found in the colon, these polyps aren’t initially cancerous. However, their similarities with adenomatous polyps mean they need to be removed once diagnosed.
- Familial polyposis coli: A rare cause of colorectal adenocarcinomas, typically associated with a specific genetic mutation (APC). If members of a family have this condition, the risk of colorectal cancer can be nearly 100% by the age of 50.
- Turcot syndrome: A condition where colorectal adenocarcinomas may come with various central nervous system tumors. The number and type of these polyps and tumors vary by individual subgroups of the syndrome.
- Cowden syndrome and PTEN hamartoma: An inherited syndrome with a wide range of symptoms, including facial skin growths, cancers in various organs such as the breast and thyroid, and gastrointestinal polyps. Regular screenings are vital to monitor these patients for malignancies.
- Peutz-Jeghers syndrome: Characterized by pigmentation changes and polyps, this condition lacks concrete evidence of a high cancer risk, but systematic screening is still advised.
- Cronkite-Canada syndrome: A rare, non-genetic disorder involving gastrointestinal polyps, hair loss, skin pigmentation, and nail issues. Major associated problems include diarrhea, malnutrition, and vomiting.
- Attenuated familial adenomatous polyposis (AFAP): A variant of FAP, patients affected by this condition usually develop a lower number of polyps later in life. More than half of these individuals are susceptible to colorectal carcinoma, which usually occurs later in life.
- Serrated polyps: These flat lesions are challenging to detect visually and were previously considered similar to hyperplastic polyps. However, it’s now understood that these lesions can develop into cancers.
Identifying and understanding the range of these polyps and polyp-related syndromes is crucial in effectively diagnosing and treating related diseases.
Possible Complications When Diagnosed with Tubular Adenoma
There are a few complications that can occur after a colonoscopy and polypectomy, such as bowel perforation, post-polypectomy syndrome, and bleeding. However, it’s important to note that the overall probability of complications arising after colonoscopies conducted for adenomas and cancer is surprisingly low — less than 4%.
Common Complications:
- Bowel perforation
- Post-polypectomy syndrome
- Bleeding
