Which vascular neoplasm is an intermediate-grade lesion caused by human herpesvirus 8?

• A. Kaposi sarcoma
• B. Hemangioendothelioma
• C. Angiosarcoma
• D. Pyogenic granuloma

Answer: (A)

Kaposi sarcoma is the vascular neoplasm caused by human herpesvirus 8, and it’s considered intermediate-grade because it can invade locally and metastasize variably—more aggressive than benign vascular lesions but not uniformly as malignant as angiosarcoma. Histologically, it shows spindle-cell proliferation forming slit-like vascular spaces with extravasated red blood cells and hemosiderin, and tumor cells typically test positive for HHV-8 latent nuclear antigen (LANA). This HHV-8 association is a hallmark that helps distinguish KS from other vascular tumors: pyogenic granuloma is benign and lobular, hemangioendothelioma is another intermediate-grade lesion not driven by HHV-8, and angiosarcoma is a high-grade, aggressive malignancy.