Skin, Kaposi sarcoma

Kaposi sarcoma (KS) is a vascular neoplasm which has several variants including classic, endemic, immunosuppressed and HIV variants. KS is well-established to be caused by the virus human herpesvirus-8 (HHV-8). Sections demonstrate a vascular lesion characterized by slit-like spaces containing red blood cells with associated red blood cell extravasation, and a spindle cell population with minimal atypia. Intracytoplasmic hyaline globules may sometimes be seen. The nodular stage shows well circumscribed nodular growth, in contrast to the flat growth seen in the patch and plaque stages. Immunohistochemistry shows CD31, CD34 and HHV-8 expression.