A patient has carcinoma on the right side of anterior 2/3rd of the tongue with lymph node of size 4cm in level 3 on the left side of the neck. Stage of the disease is

**Core Concept**
The staging of oral cancer involves assessing the primary tumor (T), lymph nodes (N), and distant metastasis (M) to determine the overall stage. In this case, we need to evaluate the extent of the primary tumor on the tongue and the presence of a lymph node metastasis in the neck.

**Why the Correct Answer is Right**
The primary tumor is located on the anterior 2/3rd of the tongue, which is a moderately differentiated carcinoma. The presence of a 4cm lymph node in level 3 on the left side of the neck indicates N2B disease. According to the AJCC 8th edition staging manual, T1 and T2 tumors are classified as Stage I, whereas T3 and T4 tumors are classified as Stage III. However, the presence of a lymph node metastasis in the neck changes the staging to Stage III.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not take into account the presence of a lymph node metastasis in the neck.
* **Option B:** This option is incorrect because it does not accurately classify the primary tumor based on its location and size.
* **Option D:** This option is incorrect because it does not consider the correct classification of the lymph node metastasis.

**Clinical Pearl / High-Yield Fact**
When staging oral cancer, it is essential to accurately assess the primary tumor, lymph nodes, and distant metastasis. The presence of a lymph node metastasis in the neck can significantly impact the staging and treatment of the disease.

**Correct Answer:** C.