Answer: Herpetic pharyngitis

Histology: At low power, the surface epithelium is extensively ulcerated and there are large geographic zones of necrosis with frank abscess formation. Expanded zones of chronic inflammation with lymphoid hyperplasia surround the abscesses. At high power, the lymphoid component consists of a mixed population of immunoblasts, plasma cells and lymphocytes. Within the necrotic debris are scattered degenerating cells with enlarged nuclei, multinucleation, nuclear molding, and occasional intranuclear eosinophilic inclusions.

Discussion: Head and neck manifestations of Herpes Simplex infection are those of an ulcerative lesion that may involve any of the intraoral sites, the nasal cavity, and the pharynx including the tonsils. The diagnosis should always be considered when dealing with an ulcer at one of these sites, and the specimen should be carefully scrutinized for the presence of viral cytopathic changes. For Herpes Simplex (types I and II), these changes include cell fusion, nuclear molding and large eosinophilic intranuclear inclusions. Immunohistochemistry is useful when this cytopathic effect is not well developed, when it is very focal, or when it is not easily distinguished from the cytopathic changes of other cytolytic viruses (e.g. CMV). Mucocutaneous disease is frequent in the HIV-positive population, and it seems reasonable to test this 19 year-old patient.