Kaposi sarcoma: What to do with a negative human herpesvirus 8 immunohistochemical stain?

Kaposi sarcoma (KS) is an intermediate vascular sarcoma that can cause significant morbidity and mortality in patients if left untreated. It is associated with human herpes virus 8 (HHV-8) infection. Definitive diagnosis is supported by classic histology including slit-like vascular spaces, spindle cells, lymphocyte infiltration, and extravasated RBCs on hematoxylin and eosin (H&E) stain and positive immunohistochemical (IHC) staining for HHV-8. We present a challenge we encountered in detecting HHV-8 by IHC in a mucosal lesion demonstrating classic histology for KS. This article is protected by copyright. All rights reserved.