**Core Concept**
Kaposi sarcoma is a vascular tumor characterized by proliferation of endothelial cells, commonly seen in immunocompromised individuals, especially those with HIV/AIDS. It presents as purple or dark blue lesions due to abnormal blood vessel formation and typically follows a multifocal pattern with potential nodal involvement.

**Why the Correct Answer is Right**
The most common site of Kaposi sarcoma is **not** the scalp. While lesions can appear on the face, limbs, or trunk, the **scalp is actually a rare site**. The majority of lesions occur on the lower extremities, face, or oral mucosa. The classic presentation includes **dark blue or purple, multifocal lesions**, and **lymph node involvement** is not uncommon, especially in advanced disease. Thus, stating that the scalp is the most common site is factually incorrect.

**Why Each Wrong Option is Incorrect**
Option B: Lesions are indeed typically **dark blue or purple** due to vascular proliferation, making this statement true.
Option C: Kaposi sarcoma is **usually multifocal**, with lesions appearing in multiple locations, which is accurate.
Option D: **Lymph node involvement** can occur, especially in the advanced stages, so this is true.

**Clinical Pearl / High-Yield Fact**
Remember: Kaposi sarcoma is **not** commonly on the scalp — it’s more often on the **legs, face, or oral cavity**. The color is due to **abnormal vascular growth**, and it’s a hallmark of immunosuppression, especially in HIV patients.

✓ Correct Answer: A. The most common site is scalp