From the Guidelines
A colorectal tumor that invades through the muscularis propria into the subserosa is classified as a T3 lesion. According to the UICC TNM staging (8th edition) classification for colon and rectal cancer, as described in the study by 1, the T staging specifically describes the depth of tumor invasion through the layers of the bowel wall. The key stages are:
- T1 lesions: confined to the submucosa
- T2 lesions: invade into but not through the muscularis propria
- T3 lesions: extend through the muscularis propria into the subserosa or into non-peritonealized pericolic or perirectal tissues
- T4 lesions: directly invade other organs or structures and/or perforate the visceral peritoneum. The distinction between these stages is important for treatment planning and prognosis, as deeper invasion correlates with higher risk of lymph node involvement and distant metastasis, as noted in the study by 1.
The correct classification of a colorectal tumor is crucial for determining the appropriate treatment and predicting patient outcomes. In this case, a tumor that invades through the muscularis propria into the subserosa falls into the T3 category, which may involve more extensive treatment, such as surgery, chemotherapy, or radiation therapy, depending on the individual patient's situation, as discussed in the guidelines by 1.
It is essential to use the most recent and accurate staging system, such as the UICC TNM staging (8th edition), to ensure consistent and reliable classification of colorectal tumors, as recommended by 1. This staging system provides a standardized framework for clinicians to evaluate the extent of tumor invasion and make informed decisions about treatment and management.
From the Research
Colorectal Tumor Staging
- The TNM classification system is used to determine the prognosis of cancer patients, with the T category reflecting the depth of tumor invasion 2, 3.
- A colorectal tumor that invades through the muscularis propria into the subserosa is classified as a T3 lesion, according to the TNM classification system 2.
- The T3 category is defined by a tumor that invades through the muscularis propria into pericolorectal tissues, and can be further subdivided into T3a, T3b, and T3c based on the depth of invasion beyond the outer border of the muscularis propria 2.
- In contrast, a T2 lesion is defined as a tumor that invades through the muscularis propria, but does not extend into the subserosa 4.
- A T1 lesion is defined as a tumor that invades the submucosa, but does not extend into the muscularis propria 5.
- A T4 lesion is defined as a tumor that invades through the visceral peritoneum or invades other organs or structures 2, 3.
Key Characteristics of T3 Lesions
- T3 lesions are characterized by invasion through the muscularis propria into the subserosa, with or without involvement of nonperitonealized pericolic tissue 2.
- The depth of invasion beyond the outer border of the muscularis propria can be measured and categorized as T3a (≤1 mm), T3b,c (>1−15 mm), or T3d (>15 mm) 2.
- The prognosis of T3 lesions varies depending on the depth of invasion, with T3d lesions having a poorer prognosis than T3a or T3b,c lesions 2.
Comparison with Other Lesions
- T2 lesions have a better prognosis than T3 lesions, with a lower risk of distant metastasis and higher disease-free survival rate 2, 4.
- T1 lesions have a better prognosis than T2 lesions, with a lower risk of lymph node metastasis and higher disease-free survival rate 5.
- T4 lesions have a poorer prognosis than T3 lesions, with a higher risk of distant metastasis and lower disease-free survival rate 2, 3.