## **Core Concept**
The TNM staging system is used to classify the extent of spread of cancer, with T representing the size and extent of the primary tumor. For oral cancer, the T classification helps in determining the prognosis and treatment plan.

## **Why the Correct Answer is Right**
The correct classification for T3 in oral cancer is a tumor more than 4 cm in greatest dimension. This classification is crucial for the management and prognosis of oral cancer patients.

## **Why Each Wrong Option is Incorrect**
* **Option A:** Tumor size less than 2 cm is typically classified as T1, making this option incorrect for T3.
* **Option B:** A tumor size between 2-4 cm is usually classified as T2, which does not match the criteria for T3.
* **Option D:** Tumor size greater than 6 cm or with specific features like invasion into adjacent structures might be classified under T4, not T3.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that accurate staging of oral cancer is critical for determining the prognosis and treatment plan. The TNM system helps in standardizing the classification and communication among healthcare professionals.

## **Correct Answer:** . Tumor more than 4 cm in greatest dimension.