S2C7P2Psoriasiform


	S2C7P2-1 (contact dermatitis): A portion of a dermal papilla is represented on the right. The rete ridge to the left shows keratinocytes of basal unit type (the long axes are perpendicular to the surface of the skin). The small area of spongiosis has acquired poorly defined, reticulated qualities; the pattern might be characterized as an incipient spongiotic vesicle. There are scattered dendritic histiocytes in the defects. Most of the cells of the defect are lymphocytes.

S2C7P2-2 (contact dermatitis): This is a psoriasiform pattern with hyperkeratosis and parakeratosis. The granular layer is prominent in areas. The rete patterns are irregular; this quality is a feature against the diagnosis of psoriasis. The papillary dermis is widened and fibrotic. The dermal papillae are club-shaped and edematous or fibrotic. Infiltrates of lymphoid cells are perivenular.

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	S2C7P3 a&b (pemphigus foliaceus): This alcian blue stain clearly delineates the boundary between the superficial and basal epidermal units. The basal unit is blue; the superficial unit is red. Both the superficial unit and the basal unit are hyperplastic. The reaction pattern is psoriasiform and spongiotic. There are small vesicles in the basal unit. There are also small vesicles in the superficial unit, but these may have formed in the basal unit and, with the kinetics of the movement of cells to the surface (with the differentiation and movement of keratinocytes to replinish cells lost at the surface), some of the vesicles have found their way to higher levels. The blue of the basal unit marks the character of the mucinous, interstitial matrix of the basal unit. Mucinous deposits are also present in the upper reticular dermis (normally, the papillae have a mucinous quality. In the center of the field, a dermal papilla is edematous and club-shaped; it contains a tortuous, dilated vessel (a common feature of psoriasiform reactions). P3b shows the mucinous avenues of the basal unit at a higher magnification (pemphigus foliaceus).

	S2C7P2-4 a&b: This example of CONTACT DERMATITIS is more uniformly psoriasiform with less prominent spongiosis. Inter-cellular spaces of the basal unit contain a loose infiltrate of lymphocytes and histiocytes. Lymphoid infiltrates extend along vessels into the dermal papillae and, in turn, migrate into the overlying epidermis. In P2-4b, the dendritic processes of histiocytes sinuously extend among keratinocytes. Lymphocytes cling to the dendrites. This is a classic pattern of cellular immunity affecting the basal epidermal unit of the reactive superficial unit.

S2C7P2-5 The pattern is spongiotic and psoriasiform but, for this example, the clinical impression was DRUG ERUPTION. The distinctions between basal unit and superficial unit can be easily identified without the aid of arrows. The cells of the superficial unit have their long axes parallel to the skin surface and the cells of the basal unit have a perpendicular orientation to the surface of the skin. The cells of the basal unit are paler (and more acidophilic) than those of the superficial unit. The pallor, in part, is secondary to intra-cellular edema. The papillary dermis is widened and pale. Focally, the dermal papillae are partially outlined along their perimeters by delicate, fibrous lamellae. There are perivascular lymphoid infiltrates which follow vessels to the dermal-epidermal interface at the tips of papillae. Lymphocytes and histiocytes have migrated into the epidermis. The superficial unit is slightly hyperplastic. The pattern in the basal unit is psoriasiform.

S2C7P2-6: At higher magnification, the dermal-epidermal interface is represented. There are vacuolar changes on both sides of the basement membrane. Lymphocytes and histiocytes, both migratory and dendritic (or “fixed”) variants, are richly represented among keratinocytes of the basal unit of the epidermis. The patterns have a reticulated quality. In this limited representation of the patterns, it would be difficult to say whether this is spongiosis, or a lichenoid pattern. The distinctions at this level are somewhat nebulous. In searching for distinctions, a lichenoid reaction generally involves a greater expanse of the dermal-epidermal interface and does so in a more diffuse pattern (DRUG ERUPTION).

S2C7P2-7 a&b: These two examples are representative of patterns seen in SEBORRHEIC DERMATITIS. The patterns are clearly spongiotic, but also have psoriasiform qualities. The psoriasiform qualities of lesions of seborrheic dermatitis are variable. The basic, spongiotic qualities of cell-mediated immunity are represented. The edema is most prominent in a hyperplastic basal unit of the epidermis. Lymphoid infiltrates extend into the areas of spongiosis. The superficial unit is thin with a poorly developed granular layer. There is a cap of parakeratotic debris over the area of spongiosis. The spongiotic vesicle of P2-7b (right) involves the intra-epidermal portion of a follicle. Similarly, but not as clearly, the area of spongiosis in P2-7a is situated close to the ostium of a follicle. These follicular components are common in lesions of seborrheic dermatitis.

S2C7P2-8: The patterns are spongiotic and psoriasiform. The granular layer is slightly accentuated. Rete ridges are broad and elongated. The papillary dermis is pale; some of the dermal papillae are club-shaped. There is faint evidence of early lamellar fibrosis outlining the elongated rete ridges (SEBORRHEIC DERMATITIS).

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