The TNM staging system is an important way to understand how severe a cancer is. One key part of this system is tumor size, which is very important for figuring things out. The "T" in TNM stands for "tumor," and it looks at how big the main tumor is and how far it has spread.

Why Tumor Size Matters:

• Local Extent: Bigger tumors often mean a more serious illness. For example, a tumor called T1 might be small (like ≤2 cm), while a T3 tumor could be larger than 5 cm.
• Spread Potential: Larger tumors are more likely to invade nearby tissues, which can allow the cancer to spread to other parts of the body.

Examples:

1. Breast Cancer:
   • A T1 breast tumor is 2 cm or smaller. T2 tumors are between 2 cm and 5 cm. Knowing the size helps doctors decide how to treat the cancer. Smaller tumors may need less intense treatments.
2. Lung Cancer:
   • A T1 tumor is 3 cm or smaller, while a T2 tumor is more than 3 cm but 5 cm or smaller. Understanding these sizes is very important for making surgery plans and deciding if other treatments are needed.

In short, tumor size is a key part of the TNM system. It helps doctors understand how a tumor might behave and what treatment options are best.