**Core Concept**
Kaposi sarcoma (KS) is a type of cancer that originates from the endothelial cells lining blood vessels. It is characterized by the proliferation of spindle-shaped cells, leading to the formation of vascular tumors. KS is associated with human herpesvirus 8 (HHV-8) infection and is commonly seen in immunocompromised individuals, particularly those with HIV/AIDS.

**Why the Correct Answer is Right**
Kaposi sarcoma typically presents with skin lesions, which can be flat or raised, and may also involve internal organs such as the lungs, gastrointestinal tract, and lymph nodes. The lesions are often purple or red in color due to the presence of blood vessels. The correct answer is likely to be one of the options that does not accurately describe a characteristic of Kaposi sarcoma.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Kaposi sarcoma is indeed characterized by the presence of spindle-shaped cells, which are a hallmark of the disease. These cells are derived from endothelial cells and are responsible for the formation of vascular tumors.

**Option B:** This option is incorrect because Kaposi sarcoma is strongly associated with human herpesvirus 8 (HHV-8) infection. The virus is thought to play a key role in the development of the disease, particularly in immunocompromised individuals.

**Option C:** This option is incorrect because Kaposi sarcoma is indeed characterized by the formation of vascular tumors, which can involve the skin and internal organs. The tumors are often composed of spindle-shaped cells and may exhibit a range of histological features.

**Option D:** This option is correct because Kaposi sarcoma is not typically characterized by the presence of squamous cell carcinoma, which is a different type of skin cancer. Squamous cell carcinoma is usually associated with UV radiation exposure and is not linked to HHV-8 infection.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that Kaposi sarcoma is a type of cancer that is strongly associated with human herpesvirus 8 (HHV-8) infection, particularly in immunocompromised individuals. This is a critical point to remember for exam purposes and in clinical practice.

**Correct Answer: D.**