Cytopathology of oral infectious diseases: do we really do our best?

Oral pathology is common in patients with immunodeficiency and up to 80% of patients with human immunodeficiency virus (HIV) infection or haematopoietic stem cell transplantation following high dose chemoand radiation therapy suffer from significant oral disease. The type of pathology varies according to the underlying condition, but infection is at the top of the differential diagnostic considerations. In addition, as infections in immunocompromised patients may rapidly develop into life threatening disease, early and accurate diagnosis is mandatory for adequate patient management. Cytopathology, as an easy to perform diagnostic procedure, has the ability to produce diagnostic results within a few hours, is a non-invasive test and is especially suited for the diagnosis of infectious diseases in this easily accessible body cavity. Therefore, cytopathologists should be familiar with the morphological aspects of the various infectious agents they may encounter at this site. In this issue of Cytopathology, Braz-Silva et al. in the group of Paul Hofman from Nice, France, supported by colleagues from the University of Sao Paolo, Brazil, provide an excellent review covering the diversity of infections inducing oral pathology. In their comprehensive overview, the authors systematically describe the type of oral lesions and the cytomorphology of a wide variety of viral, bacterial, fungal and parasitic diseases. Of note, the text covers not only the common suspects including Herpes simplex, candidiasis or mycobacterial infection, but also less commonly encountered, at least in the Western World, microorganisms such as paracoccidiomycosis and even real curiosities, for example Sparganosis, which could enter the differential diagnosis of an individual patient. The text is supported by excellent illustrations with representative figures depicting the clinical and macroscopic aspects as well as the cytopathology with high quality micrographs. In addition, the review covers methodological aspects including the differences between abrasive and exfoliative techniques for specimen collection and the data presented are covered by an adequate overview of the literature. The information and the references presented, however, bring up a few problems associated with the cytopathology of infectious diseases in the oral cavity. First, there is an obvious shortage of prospective studies with a sufficient number of patients. This is illustrated in the review by Braz-Silva et al. in their thoroughly comprehensive literature review, reporting often only small series or case reports. Considering the large number of immunocompromised patients and the high incidence of oral lesions in this patient group, this is somewhat surprising and may indicate that cytopathologists are not regularly involved in the diagnostic management of these patients and may be being consulted more by chance. Other diagnostic procedures, performed by the microbiologist or the physician in charge may be more usual as the first line approach. The posteriority of cytopathology for the diagnosis of oral infections in the immunocompromised patients may indeed have several reasons. Little is known about sensitivity, specificity and especially positive and negative predictive values for cytopathology in the diagnosis of even common infections at this site. Furthermore, the impact of auxiliary methods, especially the use of in situ techniques such as immunocytochemistry and in situ hybridization is not really well investigated. The polymerase chain reaction (PCR), widely used in the diagnosis of infectious agents, can also be successfully applied. However, one has to keep in mind that the detection of a microorganism by a highly sensitive method may not always represent disease. Finally in contrast to the cytopathology of neoplasia, the diagnosis of infections in immunocompromised patients has to be rapidly available as immediate therapeutic interventions are often required. Taken together, although cytopathology is a powerful tool for the diagnosis of oral infections, there is the impression that this technique does not really have the place it deserves as an everyday diagnostic procedure. How can we overcome this? Primarily, it is important, that cytopathologists seek direct contact with their clinical colleagues. It is a major advantage when the cytopathologist personally obtains the sample, either exfoliative or, better, by abrasion, taking samples from different areas of the lesion. Preferably on site or at least immediate interpretation is essential and covers two aspects: (1) it confirms (or not) that appropriate material has been taken and (2) it allows a preliminary diagnosis. Rapid auxiliary methods, especially immunfluorescence or immuncytochemistry for common viruses, but also for other microorganisms, should be available to ensure a definitive diagnosis within a few hours or define the further diagnostic