Inflammatory lesions.

Abstract Inflammation is classified on cytology based on the predominant cell type involved. It is subdivided into the following categories: neutrophilic, macrophagic, eosinophilic, lymphocytic and mixed (in the absence of a prevalent cell type). The recognition of the inflammatory pattern helps the pathologist to restrict the list of differential diagnoses and sometimes also to identify a potential aetiology. Inflammation can be sterile or associated with an infectious disease. However, the absence of microorganisms on cytology does not rule out an infectious cause, and further testing with a higher sensitivity (e.g. bacterial culture, polymerase chain reaction (PCR)) may be required. Inflammation may be the sole pathologic process causing the formation of the cutaneous lesion or it may be associated with hyperplastic, dysplastic and neoplastic processes. In this chapter diagnosis of skin diseases based on the following criteria namely neutrophilic inflammation; macrophagic inflammation; eosinophilic inflammation; lymphocytic inflammation; inflammation caused by infectious agents; panniculitis; xanthoma; injection site and foreign body reaction; and pemphigus foliaceus (PF) were discussed.