S2C6P1SpongioticEtc

S2C6P1-1 (contact dermatitis): The functional basal unit of the epidermis is hyperplastic (its domain, including slightly elongated rete ridges, has expanded). The papillary dermis is widened. Loose infiltrates of lymphoid cells in the perivascular spaces in the upper portion of the reticular dermis extend along the vessels into the papillary dermis. They also extend into the epidermis in areas of spongiosis. The rounded defects are spongiotic vesicles; they compress and deform neighboring keratinocytes. Blue arrows define the boundary between the superficial and the basal units of the epidermis. In defining spongiosis, attention is being paid to the fluid avenues of the basal unit of the epidermis (the epidermal interstitium).

S2C6P1-2 (contact dermatitis): In this area of intra-epidermal edema (spongiosis), the spaces among keratinocytes of the basal unit of the epidermis are widened. The basal unit is hyperplastic and the superficial unit is thin. The granular layer is not prominent. Among the keratinocytes in the area of edema, dendritic histiocytes (presumably Langerhans cells) are increased in number (blue arrows). Dendritic processes extend from these cells into the inter-cellular spaces among the keratinocytes. For reference, a green arrow identifies a small lymphocyte abutting upon a histiocyte. There are liquefactive changes at the dermal-epidermal interface.

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Inter-cellular bridges (prickles) are intact in the edematous epidermis. The clinical impression, for the lesion represented in P1-1 & 2, was contact dermatitis. The fluid avenues are widened; presumably, they are more watery than myxoid. Acid mucopolysaccharides, depending on conditions, have the ability to be watery or viscous. The dendritic cells, by their anatomic relationships, and following the release of kinins, have the opportunity to influence the nature and fluidity of the epidermal interstitium (CONTACT DERMATITIS)

S2C6P1-3: In response to a variety of insults, the basal unit of the epidermis often undergoes a distinctve form of hyperplasia. In the process, the rete patterns are accentuated; the rete ridges are elongated and are associated with elongated, club-shaped dermal papillae. The prototype for this type of epidermal response is psoriasis. Psoriasis is not characterized by significant inter-cellular edema; it is a rather pure basal unit hyperplasia with scanty infiltrates of lymphocytes. On the other hand, lesions of psoriasis are characterized by a mild hyperplasia of dendritic histiocytes (Langerhans cells) in the expanded basal unit. It is a paradox of the reaction in the epidermis of a lesion of psoriasis, that the histiocytes do not attract lymphocytes into the epidermal domain, even though the basal unit undergoes hyperplasia. In the common allergic disorders, which are characterized by psoriasiform patterns, spongiosis is common and the intra-epidermal histiocytes are associated with loosely spaced lymphoid cells, usually in close association with the histiocytes (a variation of the rosette of cell mediated immunity). In the bottom drawing, the rounded defects are two spongiotic vesicles, each of which contains one Langerhans cell, one lymphocyte, and one histiocyte.

S2C6P1-4: The features of a common spongiotic and psoriasiform reaction are represented (contact dermatitis). There is focal parakeratosis with an intra-corneal, spongiotic vesicle (red arrows). The granular layer is interrupted in the area of parakeratosis (and inter-cellular edema). There is hyperplasia of the basal unit with elongation of the rete ridges. The expanded, bulbous rete ridges have partially compressed the dermal papillae into a club-shaped configuration. Green arrows outline an edematous, club-shaped papilla. Its vessel is dilated; there are scanty, loose perivascular infiltrates of lymphoid cells. There are mild perivascular infiltrates of lymphoid cells in the upper portion of the dermis. This pattern, like that of spongiotic dermatitis, is representative of a reaction affecting the reactive superficial unit of the skin (a reaction involving the epidermis and the papillary dermis as a unit). In these examples, the reaction is mediated by lymphocytes and histiocytes; the reaction is primarily at the level of the epidermal domain of dendritic histiocytes (CONTACT DERMATITIS).


		S2C6P1-5 a&b (contact dermatitis): The pattern in P1-5a, to the left, is both spongiotic and psoriasiform. There is a localized area of inter-cellular edema. In addition, some of the keratinocytes show cytoplasmic vacuoles (intra-cellular edema). The inter-cellular edema extends to the keratin layer (and a zone of parakeratosis). The red arrows identify migratory histiocytes (histiocytes newly arrived in the epidermal domain). A green arrow points to a dendritic histiocyte (presumably a differentiated histiocyte and presumably a Langerhans cell). Most of the keratinocytes in this field are respresentatives of the basal epidermal unit. In P1-5b, intra-and inter-cellular edema are prominent features. The small spongiotic vesicle (the rounded defect) is in the superficial unit of the epidermis. It is unlikely that it formed in this location. The spongiotic reaction initially affects the basal unit of the epidermis. A vesicle in the superficial unit, or the keratin layer probably has found its way there, in the process of terminal differentiation, by moving in concert with neighboring keratinocytes from the basal unit into the superior unit and, thence, into the keratin layer. Cells are delivered to the superficial unit in concert with the intra-epidermal vesicle. The arrows identify histiocytes in the vesicle (CONTACT DERMATITIS).

		S2C6P1-6 (contact dermatitis): At the top of the field a small portion of the superficial unit is represented. The cells of this unit are larger (have more abundant cytoplasm) than those of the edematous basal unit. In the basal unit, the cells are more vertically oriented and inter-cellular spaces are better defined. In part, these qualities may reflect the differences in the nature of the inter-cellular spaces. In the superficial unit, the spaces are occupied by lipid rich membranes; the spaces are relatively closed. In the center of the field, at least 3 dendritic histiocytes are represented, and at least 2 of these cells appear to lie in lacunae.

S2C6P1-7 a&b (contact dermatitis): This lesion of acral skin (P1-7a) has a hypertrophic quality. The components of the reactive superficial unit (namely, the epidermis and the papillary dermis) are hyperplastic. There is mild papillomatosis. Rete ridges are elongated and the epidermal pattern is markedly psoriasiform. In turn, dermal papillae are elongated; some appear to be club-shaped. Perivascular lympoid infiltrates are most prominent in the tips of dermal papillae. The papillary dermis also appears to be fibrotic (optically dense and more brightly acidophilic). In P1-7b, there is a zone of marked edema affecting the basal unit of the epidermis at the tip of an inflamed dermal papilla. Lymphoid infiltrates extend in continuity from the edematous tip of the papilla into the overlying basal unit. The infiltrating cells are mostly lymphocytes, but there are scattered dendritic histiocytes and probably a few migratory histiocytes. This is a classic pattern of a cell-mediated, immune reaction. The reactive superficial unit of the skin is hyperplastic. The patterns might be characterized as compensatory hyperplasia and hypertrophy. The hypertrophic character of the patterns in P1-7 might be cited as evidence of chronicity.

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