Abstract
Kaposi sarcoma (KS) is a vascular and lymphatic neoplasm caused by human herpesvirus 8 (HHV-8). AIDS-related KS has variable clinical courses ranging from mild disease presenting as an incidental finding to severe disease presenting as an aggressively progressing neoplasm that can lead to poor prognosis or even death. Typical clinical manifestation of KS is known as multiple cutaneous lesions on the extremities, trunk, and face with mucosal involvement. A 46-year-old male with AIDS complained of an erythematous patch on the right forearm which appeared 5 months ago. For a year, he was treated with antiretroviral drugs for AIDS. Physical examination revealed a 2.5-cm solitary erythematous patch only on the right forearm. Laboratory data revealed human immunodeficiency virus (HIV)-1 RNA of less than 40 copies/ml and a CD4 cell count of 264 cells/mm(3). Histological examination revealed numerous slit-like spaces and vascular proliferation with primitive blood vessels dissecting between the collagen bundles and the dermis. Immunohistochemical staining showed positive HHV-8 nuclear staining of spindle cells. The histological features and positive HHV-8 immunohistochemical stain were consistent with the diagnosis of early patch stage of AIDS-related KS. KS can readily be misdiagnosed in early patch stage even by experienced clinicians, which leads to requirement of pathologic determination. On close inspection, it can be distinguished from other mimickers by its distinctive histologic features and immunohistochemical staining for HHV-8. Therefore, in cases of HIV-positive patients with clinically or histologically vascular-appearing mucocutaneous lesions, KS should be considered as a possible differential diagnosis.