Pictorial 3

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Melanocytic Dise ase.

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SextrC13P1-1: This is a lichenoid lymphocytic vasculitis with representation of the changes in the epidermis and along the dermal-epidermal interface. The blue arrows define an interface between the basal unit and the superficial unit of the epidermis. In this area, the epidermal infiltrates of inflammatory cells are relatively limited to the altered basal unit. The pattern in this area might be characterized as a “primary” lichenoid reaction. In this type of response the basal unit is relatively preserved and in some examples may even be hyperplastic. Orange arrows point to wavy, loosely arranged acidophilic fibers; these fibers are markers for reduplication of the basement membrane. To the left of the center of the field, the epidermal pattern is altered. There is no basal unit (a multilayered collection of similar cells) as such. The pattern can only be characterized as a hypertrophy (and perhaps hyperplasia) of the superficial unit. The superficial unit is concerned with terminal differentiation; the kinetics in the superficial unit promote the formation of an impervious barrier along the surface of the skin. In hypertrophies of the superficial unit there is hypertrophy of cells of the granular layer; the end-product usually is a compact hyperorthokeratosis. As seen in the right side of the field, an hypertrophied superficial unit is also a defense against native but aggressive inflammatory cells. In the basal unit, intercellular spaces are open; inflammatory cells find open avenues to invade. In the superficial unit, particularly an hypertrophied superficial unit, a lipid-rich membrane has closed the intercellular avenues; inflammatory cells are denied access to the intercellular spaces. In this manner, an hypertrophied superficial unit preserves epidermal intergrity in the face of an assault by aggressive inflammatory cells (secondary lues).

 

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