Inflammatory Cutaneous Lesions
The inflammatory lesions of the skin may be solitary and constitute by themselves the whole diagnostic problem faced by the microscopist. On the contrary, they may be multiple, representing part of a cutaneous disease or of a systemic condition involving
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Inflammatory Cutaneous Lesions
The inflammatory lesions of the skin may be solitary and constitute by themselves the whole diagnostic problem faced by the microscopist. On the contrary, they may be multiple, representing part of a cutaneous disease or of a systemic condition involving several organs, including the skin. At the time inflammatory lesions of the skin are removed for microscopic examination, they may be in an evolutive phase or otherwise, after having ended that stage without complete reestablishment of the affected area, they may be in a postevolutive, inactive phase. Still some other lesions, at the time of their removal, may be in a transitional phase at the end of which, if they had not been previously removed, they may have had eventually emerge as overt malignancies. Accordingly, three Subdivisions of inflammatory lesions are recognized in this classification. These are referred to as evolutive, postevolutive, and transitional. In order to establish a first separation among the evolutive inflammatory lesions, a topographic criterion was adopted. In this way, five Classes of them may be recognized, which are the ones with epidermal, junctional, dermal, subcutaneous, or adnexal localization. Evolutive lesions, however, are localized only with rare exceptions. Instead, they affect surrounding areas of the skin with variable intensity. For this reason, to each of the postulated five Classes, resulting from a rather rigid approach, the prefix “predominant” must be attached to adapt the classification to reality. In the case of the postevolutive lesions, the alterations suffered by the tissues during the active inflammatory process along with vascular proliferation, collagen deposition, and other reparative changes deeply distort the affected site, erasing the microscopic hallmarks on which the previous taxonomic scheme was based and making necessary another approach for their classification. In this way, dystrophic, atrophic, and cicatricial lesions are recognized (Fig. 5.1). Insofar as the transitional lesions, they are arranged at the end of this chapter in three separate Groups of histiocytic, Langerhans, and T cell lesions. Concerning the pathogenesis of the inflammatory cutaneous lesions, either isolated or as part of more complex nosologic E. Zappi, E.A. Zappi, Dermatopathology, DOI 10.1007/978-1-4471-2894-6_5, © Springer-Verlag London 2013
processes, several factors may be responsible. Among them should be mentioned physicochemical agents such as UV radiations, heath and cold, acid and basic solutions, and traumas of every sort which the skin, due to its exposed situation, may ineludibly confront. Following physicochemical agents, viruses must be considered. Figure 5.2 presents the group of viruses of major importance regarding dermatopathology. After viruses, the next agents to be mentioned in cutaneous pathology are bacteria, arthropods and other ectoparasites, and, finally, adverse immune reactions. These deserve a special comment. Although the immune system is primordial for the defense of
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