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INTRODUCTION
(continued)
INFLAMMATORY DISEASES OF THE SKIN
(HISTOLOGIC REACTION PATTERNS)
Skin is a remarkably adaptable organ. As both a barrier and an interface, the skin of man physically defines his natural limits.
Texture and color, on the one hand, and molding of the skin to accommodate the contours of the skeleton, on the other, most often provide the features by which we initially judge one another. Emphasis on these most
superficial, and even fleeting, qualities has promoted a culture in which vanities are indulged. Much of what passes for modern dermatology is an exploitation of our vanities.
Man interacts with a hostile environment; the encounters are damaging in varying degrees. The insults variably involve the organ
systems, but skin is particularly exposed; the results of injuries to the skin are readily appreciated; the investing nature of the skin facilitates an evaluation of its reactions to injury.
Inflammation is the common response of the skin to injury. The signs and symptoms of inflammation include tumor, rubor, calor, and
dolor (swelling, redness or discoloration, heat, and pain). Although these signs are emphasized in the diagnosis of infectious diseases, they retain some relevance in the diagnosis of a variety of inflammatory, but
non-infectious, cutaneous processes. In aggregate, they are limitedly simple, and yet the physical signs and symptoms of the cutaneous inflammatory diseases are remarkably complex; the protean character of the
combinations finds expression in a bewildering array of clinical designations. The interpretation of relevant histologic patterns is complicated, not only by a plethora of usurped, clinical designations, but also by
the need to adapt these designations to temporal variations in histologic patterns. A dermatologist is likely to think in clinical terms, especially when encountering a disease for which its designation mainly has
clinical relevance. A pathologist, when faced with similar handicaps, is likely to bewildered. For any particular disease process, the age of a particular lesion, at the time of the initial removal of tissue for
histologic examination, has relevance for the interpretation of both clinical presentations and histologic patterns; the age-related variations in the evolution of lesions require taxonomic accommodations.
Historical Background
Progress in the classification of inflammatory diseases of the skin began in earnest at the turn of the last century with the
recorded observations of dedicated clinicians. In these efforts, histologic patterns were correlated, in a retrospective fashion, with clinical findings. A clinical diagnosis, having once been established, would
then form the basis for the promotion of correlative histologic criteria. Eventually, pathologists, from their stores of histologic criteria, were able to structure compartments of virtual images; each compartment
had some sort of relationship to one, or several, clinically defined disorders. Even with these refinements, histologic interpretations often were essentially ancillary, and confirmatory. If certain clinical
criteria were satisfied, the respective histologic changes could, and would, be anticipated. In this approach, the histologic criteria generally were virtual; they were stored images that had relevance for the clinical impression. Upon recall, the virtual images would be imposed on the histologic patterns (“impositional” taxonomic approach); the pathologist would first “see” but, then, in a submission to the clinical impression, would report what he should “see.” This remains a common practice.
The taxonomy of the histopathologic categories of inflammatory diseases of the skin are burdened with clinically relevant, but
histologically irrelevant, designations. Impositional dermatopathologic taxonomy restricts the options for the conceptualization of disease. In the mid-fifties, emphasis began to shift from the primacy of clinical
findings to correlations of clinical, laboratory, and histologic findings. Although for many disorders the laboratory has become a critical source of diagnostic data, only rarely can this data be considered
definitive in the absence of clinicopathologic correlation.
General pathologists have had to move away from a total reliance on morphology at a light microscopic level. On
occasion, they are asked to relate histologic findings to sub-microscopic findings. We are then required to believe that nature can dissect the epidermis from the dermis in such a delicate fashion that a
sub-microscopic membrane, a space, specialized filaments, or sharply localized, specific antigens can be defined as the site of the separation. We are required to define neoplasms and inflammatory diseases by cell
marker studies in which cellular organelles and filaments are identified as the defining antigens. In fact, specificity is obtained only when the marker studies are correlated, not only with microscopic findings,
but also with clinical findings and behavior. With immunohistochemical markers, we have developed sensitive special stains. With all this, human intervention is required to make results meaningful.
The illustrations in this presentation are of variable quality, they generally would be unacceptable to a
demanding editor. Perhaps, in choosing levels of pixels, I have placed too great an emphasis on facility and speed in moving about on this structured presentation. Reliance on many old transparencies, and on old
histologic preparations also might be cited as a shortcoming but, on the other hand, it would be difficult to assemble some of this material, if I depended solely on fresh, or current, material. I believe that, even
with the acknowledged handicaps, some pathologists on viewing some of the photomicrographs might find themselves lingering with a view of, and delighting in, some of the images. There is, in this presentation, some
of the mystery that makes pathology a rewarding endeavor.
Kalish RS: Antigen processing: the gateway to the immune response. J Am Acad Dermatol 1995;32: 640-52.
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