Patterns and mechanisms of inflammatory skin conditions: the pathologist’s survival kit

The diagnostic approach for inflammatory skin conditions depends primarily on pattern recognition, which is the result of the damaging agent, the tissue reparative response, the time and intensity of the lesion. For this analysis, it is essential: - Cellular response (cell perpetuation pathway, cell differentiation pathway, and activation of “default” cell death pathway) - Tissue effects (parenchymal and stromal interactions) - The combination of findings depending on the primary damage target The patterns are the result of the interaction of injury agents and tissue response, modulated in intensity and time - Elementary lesions will depend on: * primary epidermal reaction (based on cellular turnover and maturation), vascular and cellular inflammatory components, * types of cells, and * distribution of cells (topography and microanatomy) - The activity should be evaluated a from target damage (epithelial necrosis, vasculitis), exocytosis (neutrophilic), and density of infiltrate - Morphological and clinicopathologic correlation should be included in the conclusion