The cytopathology of infectious diseases.

Utilizing abrasive, exfoliative, and fine-needle aspiration techniques to diagnose infectious organisms by cytopathologic means is common practice. The increase in the number of immunosuppressed patients in conjunction with the relative ease with which specimens are procured has resulted in the need for rapid interpretation to ensure prompt and adequate treatment. Although some organisms cannot be definitively classified on cytologic preparations, morphologic clues that can guide the pathologist toward rendering a diagnosis helpful to clinicians are often present. In addition, some fungi and parasites rarely identified in cytopathology in the past are more frequently found in cytologic specimens today. This review focuses on organisms found in the United States. Special attention is paid to the morphologic findings on routine Papanicolaou- and Diff Quik-stained cytologic preparations and readily available special stains.