From the Guidelines
Tubular adenomas typically do not metastasize, and the risk of malignant transformation is very low compared to other adenoma types. These are benign polyps found in the colon that have a low risk of malignant transformation, as supported by the guidelines from the American Cancer Society and the US Multi-Society Task Force on Colorectal Cancer 1. While tubular adenomas can potentially develop into adenocarcinomas if left untreated for many years, they do not directly metastasize while in the adenoma stage. The risk of malignant transformation increases with larger polyp size (>1 cm), villous histology, and high-grade dysplasia, but pure tubular adenomas have the lowest risk among adenoma types, as noted in the guidelines for colonoscopy surveillance after polypectomy 1.
Some key points to consider include:
- The rate of carcinoma and high-grade dysplasia is very low or low in subcentimeter adenomas, reported at 0.05% for diminutive polyps and 0.9% for 6- to 9-mm polyps 1.
- Adenomas >25 mm have a 22.5% chance of containing invasive cancer or high-grade dysplasia, and polyps ≥10 mm have an 8% chance of progressing to invasive cancer at 10 years, which increases to 24% at 20 years 1.
- Regular colonoscopy surveillance is recommended following tubular adenoma removal, with intervals typically ranging from 3-10 years depending on the number, size, and characteristics of the polyps found, as outlined in the guidelines for screening and surveillance for the early detection of colorectal cancer and adenomatous polyps 1.
- If a pathology report mentions metastasis in relation to what was thought to be a tubular adenoma, this would indicate that the lesion had already progressed to adenocarcinoma with invasion beyond the muscularis mucosa, and further staging and treatment would be necessary, as discussed in the guidelines for colonoscopy surveillance after screening and polypectomy 1.
Overall, the management of tubular adenomas should prioritize prevention of malignant transformation and metastasis through regular surveillance and removal of polyps, as supported by the guidelines from the American Cancer Society and the US Multi-Society Task Force on Colorectal Cancer 1.
From the Research
Tubular Adenoma Metastasis
- There is limited information available on the metastasis of tubular adenomas, as they are typically considered benign neoplasms 2, 3.
- However, a study reported two rare cases of adenocarcinoma of the upper urinary tract arising in the background of tubular adenoma with high-grade dysplasia, suggesting a possible adenoma-carcinoma pathway in the urinary tract 4.
- Another study discussed the importance of distinguishing primary adenocarcinoma of the bladder from other glandular lesions, including benign and malignant entities, to ensure accurate diagnosis and appropriate clinical management 5.
- Metastatic cancer is a significant concern, as it is almost always terminal and accounts for more than 90% of cancer deaths, highlighting the need for understanding the mechanisms of cancer metastasis 6.
- The current literature on tubular adenomas is limited, with only a few case reports and small series available, making it challenging to determine the risk of metastasis associated with these neoplasms 2, 3.