A bullous variant of Kaposi's sarcoma in an elderly female.

We report the case of Kaposi's Sarcoma (KS) in an elderly Italian female that has slowly progressed and evolved clinically with bullous formation. The skin biopsy was diagnostic of KS, showing the typical spindle cell formations, but at the same time showing a labyrinth-like collection of vessels that correlated with the bullous nature of the clinical lesions. Immunohistochemical staining for factor VIII antigens demonstrated strong reactivity of non-neoplastic blood vessel endothelium but virtually no staining of tumor cells. This is similar to the reactivity of normal lymphatic endothelial cells and supports the notion that these labyrinth-like vessels are derived from lymphatic endothelium.