Pathology of infectious diseases: what does the future hold?

The demand for expertise in pathology for the diagnosis of infectious diseases (ID) is continually growing, due to an increase in ID in immunocompromised patients and in the (re)-emergence of common and uncommon diseases, including tropical infections and infections with newly identified microbes. The microbiology laboratory plays a crucial role in diagnosing infections, identifying the responsible infectious agents and establishing sensitivity of pathogens to drug therapy. Pathology, however, is the only way to correlate the presence of an infectious agent with the reaction it evokes at cell and tissue level. For pathologists working in the field of ID pathology, it is essential to dispose of competence in cell and tissue pathology as well as in microbiology. Expertise in ID includes understanding of taxonomy and classification of pathogens as well as morphological criteria supporting their identification. Moreover, ID pathologists must master the methods used to detect pathogens in fixed cell and tissue samples, notably immunohistochemistry, in situ hybridization and the polymerase chain reaction. Paradoxically, the increasing frequency of lesions caused by pathogens and diagnosed in a pathology laboratory appears to be paralleled by a gradual loss of expertise of pathologists in the field of infectious and tropical diseases. We contend that this may be due at least in part to the continuously increasing number of samples of tumor tissue pathologists deal with and the rapidly expanding number of tissue based biomarkers with predictive value for new anti-cancer therapies. In this review, we highlight current and future issues pertaining to ID pathology, in order to increase awareness of its importance for surgical and molecular pathology. The intention is to contribute to the development of best practice in ID pathology.