Abstract
This report describes the use of fine needle aspiration (FNA) cytology to make a rapid diagnosis of Penicillium marneffei infection in an HIV positive patient. P marneffei is a thermally dimorphic fungus that is a mould at 25 degrees C and a yeast at 37 degrees C. It multiplies by fission. It can be easily mistaken for various other infections that are characterised by the presence of histiocytes with phagocytosed yeast cells. In smears the demonstration of yeast cells with a distinctive central septum confirms the diagnosis.