## **Core Concept**
The question tests the understanding of the metastatic pattern of carcinoma of the tongue, specifically focusing on hematogenous (bloodstream) spread. Carcinoma of the tongue, a type of oral cancer, can metastasize through both lymphatic and hematogenous routes. The likelihood of hematogenous metastasis is influenced by the tumor's location and its proximity to vascular structures.

## **Why the Correct Answer is Right**
The correct answer, **D.**, involves understanding that hematogenous metastasis is more likely when the carcinoma is located in areas with direct access to the bloodstream or in regions where venous drainage directly feeds into the systemic circulation or major venous sinuses. The tongue's venous drainage is primarily through the lingual veins into the internal jugular vein and then into the superior vena cava, which leads to the right atrium. This pathway facilitates the spread of cancer cells into the systemic circulation.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because lymphatic spread is more common and initial in the carcinoma of the tongue, especially for more anterior parts.
- **Option B:** This option does not directly relate to the increased likelihood of hematogenous spread compared to the involvement of specific vascular or highly vascular areas.
- **Option C:** While this could potentially be a site for hematogenous spread, it is less directly related to the specific increased risk compared to the correct answer.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the posterior part of the tongue, due to its rich vascular supply and direct venous drainage into the internal jugular vein, poses a higher risk for hematogenous metastasis. This is a critical consideration in the staging and management of tongue carcinomas.

## **Correct Answer:** D. Base of the tongue.