From the Guidelines
Tubular adenomas are considered benign tumors, but they have the potential to develop into colorectal cancer if left untreated over time. These growths are a type of polyp that typically develop in the colon or rectum and are characterized by their tubular glandular structure when examined under a microscope. The risk of malignant transformation is related to the size of the adenoma (larger than 1 cm poses higher risk), the presence of high-grade dysplasia, and the villous component (pure tubular adenomas have lower risk than tubulovillous or villous adenomas) 1.
When discovered during colonoscopy, these polyps are typically removed completely through polypectomy to prevent potential progression to cancer. After removal, patients usually require follow-up colonoscopies at intervals determined by the number, size, and histology of the adenomas found, as the presence of these polyps indicates an increased risk for developing additional adenomas or colorectal cancer in the future. According to the most recent guidelines, patients with one to two small tubular adenomas are considered low risk and can have follow-up colonoscopy delayed for at least 5 years, and possibly up to 10 years, similar to the average-risk population 1.
Some key points to consider when evaluating tubular adenomas include:
- The adenoma-carcinoma sequence is believed to typically take more than 10 years to complete in sporadic cancers 1
- The presence of high-grade dysplasia in an adenoma should be noted by a pathologist, as it increases the risk of malignant transformation
- Adenomas can be characterized by tubular versus villous histology, with the overwhelming majority being tubular
- Lesions with >25% villous elements are termed tubulovillous and those with >75% villous elements villous, and are associated with increasing size of adenomas and higher risk of cancer.
Overall, while tubular adenomas are benign, they do have the potential to develop into colorectal cancer, and regular follow-up colonoscopies are necessary to monitor for any changes or development of new adenomas. The most recent and highest quality study recommends that patients with one to two small tubular adenomas can have follow-up colonoscopy delayed for at least 5 years, and possibly up to 10 years 1.
From the Research
Tubular Adenomas
- Tubular adenomas are a type of polyp found in the colon and rectum, and are generally considered to be benign 2, 3, 4.
- According to a study published in 2019,90% of small (1 cm) polyps were found to be tubular adenomas, and none of the polyps without dysplasia developed into malignancies 2.
- Another study published in 2020 found that patients with nonadvanced adenomas, which include tubular adenomas, did not have a significant increase in risk of colorectal cancer 3.
- A study published in 2006 found that primary care physicians recommend postpolypectomy colonoscopic surveillance more frequently than is recommended by practice guidelines, especially if the colonoscopy showed a hyperplastic polyp or a single small adenoma, which may include tubular adenomas 4.
- It's worth noting that while tubular adenomas are generally benign, they can still have the potential to develop into malignancies, and regular surveillance is recommended to monitor their growth and development 2, 3, 4.
Comparison to Other Types of Adenomas
- Tubular adenomas are distinct from other types of adenomas, such as villous or tubulovillous adenomas, which have a higher risk of malignancy 2, 3.
- A study published in 2018 discussed the rare diagnosis of tubular adenomas of the breast, which are also considered to be benign tumors 5.
- Another study published in 2004 discussed the indications for colorectal resection for adenoma before and after polypectomy, and noted that the decision for surgical resection depends on the risk of malignancy and the patient's wishes 6.