Unique histologic variants of cutaneous Kaposi sarcoma

BACKGROUND: Kaposi sarcoma (KS) is a low-grade angioproliferative neoplasm derived from lymphatic endothelium. Lesions progress from early patch stage into plaques that ultimately form tumor nodules. Several histological variants of KS have been described. The aim of this study is to describe 5 new histopathologic variants of cutaneous KS. METHOD: Skin biopsy material submitted to a South African dermatopathology practice diagnostic of KS was reviewed. Formalin-fixed, paraffin-embedded tissue was routinely processed and stained with hematoxylin and eosin. Confirmatory immunohistochemical stains included CD31 and latent nuclear antigen-1 (human herpesvirus 8). RESULTS: All biopsies were procured from HIV-positive patients with a clinical diagnosis of cutaneous KS tumor. Five distinct histologic KS variants, not previously well characterized in the literature, were identified including glomeruloid KS, telangiectatic KS, ecchymotic KS, KS with myoid nodules, and pigmented KS. Tumor cells in all of these variants were immunoreactive for CD31 and latent nuclear antigen-1. CONCLUSIONS: These unique cases highlight the ability of KS to exhibit variable histomorphology. Their clinical significance requires further study. Dermatopathologists should be aware of these newly described variants to avoid the potential for their misdiagnosis