The virus is present in tumour cells, tracks tightly to and precedes the presence of disease. Latent infection but a switch to the lytic phase may be responsible for the formation of lesions. KS is a disfiguring skin cancer which is particularly common in AIDS patients. It is a peculiar neoplasm containing many different cell types. Possibly paracrine in origin.
Spindle cells are dominant but there are also infiltrating inflammatory cells and vascular elements.
In the immunocompetent the tumour is indolent and localised. In the immunocompromised it is more widespread, disfiguring and possibly fatal. Restoration of the immune system can result in arrest and even remission. The spindle cells are not fully transformed but do grow and secrete proinflammatory and angiogenic factors. HHV8 appears to be the agent responsible for promoting spindle cell growth.