S6C20P14-Cicatricial Pemphigoid

S6C20P14-1: This vesicular lesion of cicatricial pemphigoid is relatively cell-poor at the dermal-epidermal interface; it displays some degree of “tenseness.” Dermal papillae are preserved along the floor. The roof is thin and the keratin layer little altered. The basic patterns in this lesion do not allow for a histologic distinction between bullous and cicatricial pemphigoid. The patterns might identify this lesion as an example of an early (young) expression of cicatricial pemphigoid (Compare overall morphology with that seen in a lesion of EBD [S6C31P25-2]).

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S6C20P14-2: This subepidermal bulla of cicatricial pemphigoid shows irregular degeneration of keratinocytes in the superficial unit forming the roof of the bulla. In some areas, the roof is necrotic. On the right, the superficial unit-like character of the roof of the vesicle is obvious; there is a band-like area of early coagulative necrosis along the inferior surface of the roof (the coagulated cells are anuclear; the pigment in this zone is clumped melanin). Along the surface of the floor of the defect, fibrin is condensed. A zone of granulation tissue has formed beneath the fibrin. It shows patterns of maturation and is most fibrotic near the interface between altered papillary dermis and reticular dermis. The band of vascularized fibrous tissue is organizing granulation tissue which has altered (replaced) the original matrix of the papillary dermis. The zone in which the dermis is fibrotic provides validation for the clinical designation, cicatricial pemphigoid; the clinical designation has application for a histologic pattern. Cicatricial pemphigoid is a fibrolytic and organizing pemphigoid. Pemphigoid is IgG mediated, bullous, interface dermatitis of common type, finding specificity at the level of the stratum lucidum of the basal lamina.

S6C20P14-3: At higher magnification, the keratin layer is not significantly altered. The superficial unit of the epidermis is slightly hyperplastic. The basal unit of the epidermis remains as a portion of the roof of the bulla, but shows degenerative changes. The cells of the basal unit have pale acidophilic cytoplasm and shrunken hyperchromatic nuclei (a degree of pyknosis). There is loss of nuclear polarity and many of the degenerating keratinocytes are pigmented (melanin). There is a zone of condensed fibrin along the surface of the floor of the bulla. Focally, neutrophils are clustered in the crevacies among the denuded dermal papillae. The papillary dermis is widened and delicately fibrotic. Near the interface between the connective tissue of the papillary dermis and the condensed fibrin, the connective tissue is pale. This may simply be edema but alternately might represent some degree of stromo- or fibro-lysis, affecting both basement membrane and adjacent connective tissue (stroma). The condensed fibrin will also be given an accounting in the following presentation (cicatricial pemphigoid).

S6C20P14-4: The red arrows represent an attempt to define the interface between condensed fibrin and the basement membrane zone of the altered papillary dermis. There is a proliferation of mesenchymal cells (fibroblasts) in the papillary dermis (activation of connective tissue cells). Most of the inflammatory cells are histiocytes; many of these cells contain deposits of melanin in the cytoplasm. There is a bipolar spindle cell at the tip of a red arrow near the center of the field. In part, a polar extension of this cell projects into the condensed fibrin. This is an extension beyond the limits normally defined by the basement membrane. The pattern is acceptable as evidence that mesenchymal cells have taken the initial step leading to the organization of condensed fibrin; they are invading it. In this approach, one of the major defects leading to organization of fibrin is a failure of the inflammatory process to digest the condensed fibrin. This failure brings to mind the significance of the “crisis” in determining the resolution of alveolar exudates in the progress of pneumococcal pneumonia. If the crisis does not occur, the exudate is not resorbed and fibrous tissue is deposited in the alveoli. In this manner, the alveolar space becomes obliterated by newly formed fibrous tissue.

 

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