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S2C10P4-1 & 2 (to left) (geographic tongue, annulus migrans, migratory glossitis): In the first photo to the immediate left, a lesion of the tongue is represented. The pattern is psoriasiform and even hypertrophic. There is an abnormal keratinized product at the surface and rete ridges are regularly elongated. Dermal papillae are slightly club-shaped. In figure to the right, neutrophils have collected in the upper portion of the superficial unit of the epithelium and in the parakeratotic cap. There are lytic defects in which neutrophils have collected; the lesion has spongioform pustular qualities.

S2C10P4-3 a & b (migratory glossitis): Clinically, this lesion manifested the qualities of migratory glossitis. The patterns are psoriasiform and spongioform pustular. The villous patterns in part are a manifestation of the lytic effects of the spongioform process along the surface of the mucous membrane. The cytoplasmic pallor of some of the cells in P4-3b (above and to the right) is evidence of the cytolytic process that results in the formation of lytic defects outlined by keratinized remnants of cell walls. Presumably, the neutrophils are the mediators of the lytic process.

Psoriasiform processes affecting the mucous membranes commonly manifest spongioform pustular qualities. Psoriasis is included in this group. Annulus migrans is a term that is sometimes offered as a designation for the oral manifestations of psoriasis. In an idiopathic category, similar histologic patterns have been characterized as migratory glossitis, or geographic tongue. Superficial fungus infections, affecting mucous membranes, commonly have spongioform qualities. Lesions of secondary syphilis on mucous membranes (condyloma latum) also manifest spongioform pustular features.

S2C10P4-4 a & b (subcorneal pustular dermatosis): The epidermis shows irregular acanthosis (hyperplasia of keratinocytes) and irregular rete patterns. In P4-4a (to the left), there is a subcorneal defect to the right of the center of the field. The keratin layer is relatively normal; this speaks for a process that is fairly acute. The papillary dermis is widened and relatively clear (it is edematous). Several lytic defects are present in the dermis and are perpendicular to the surface of the skin; they are section artefacts related to defects along the edge of the knife of the microtome. In P4-4b, the subcorneal defect is shown at higher magnification. The small cells, loosely clustered in the defect, are neutrophils. There is a subtle pattern of acantholysis along the floor of the defect. Some of the keratinocytes along the floor of the defect have detached from their neighbors and are free; they are rounded in outline. This loss of cellular cohesion is usually accompanied by rounding-up of the detached cells and by increased cytoplasmic acidophilia (acantholysis and dyskeratosis). Small lytic defects in the epidermis near the floor are present among keratinocytes; some of these defects contain inflammatory cells (i.e., neutrophils). The lesion has some features of a poorly developed spongioform pustule.

S2C10P4-4c (continued): At the margin of the subcorneal pustule, neutrophils have collected in lytic defects among viable keratinocytes. The patterns in this area are clearly spongioform and pustular; they provide a variant psoriasiform quality.

Prominently and regularly elongated rete ridges are not a uniform feature of psoriasiform disorders. Some show less in the way of alterations in rete patterns, but show acanthosis and variable alterations in the character of both the superficial unit and the keratin layer. It is conceptually possible to link some of the subcorneal vesicular, or pustular disorders with the psoriasiform disorders. The patterns in P4-4 are those of a subcorneal pustule and the related disorder in this case is subcorneal pustular dermatosis. This is not simply a play on histologic patterns, but is an admission that a relationship between psoriasis and subcorneal pustular dermatosis is recognized, but ill-defined. Minor differences in the manner in which migrant neurtrophils in the epidermis affect the integrity of the native domain of keratinocytes significantly affect the nature of histologic patterns.

S2C10P4-5 a & b (to the left) (impetigo herpetiformis):  In this example of a subcorneal pustule, the keratin layer is relatively normal, but detached centrally. The subcorneal defect contains fibrin and degenerating neutrophils. Rete patterns are accentuated; the papillary dermis is widened and edematous. Although not richly cellular, the epidermis along the floor of the defect 9to the right shows lytic defects that are outlined by keratinized cell membranes. Neutrophils are present in some of the defects.

In practice, it is not always possible to positively assign histologic patterns to specific clinical categories. Clinicopathologic correlations will be required. For a lesion showing this pattern, special stains for organisms would also be indicated.

S2C10P4-6 (bullous impetigo): In pursuing variations in the category of subcorneal defects, some examples may not be associated with significant inflammatory infiltrates. When faced with such cell-poor examples, the acantholytic disorders, specifically pemphigus foliaceus, should be considered. On the other hand, some infectious disorders may not be regularly associated with significant inflammatory infiltrates. The lesion above is an example.

Some infectious disorders affecting the epidermis can be relatively cell-poor. A Gram stain may occasionally be an aid in the diagnosis of some of these sub-corneal disorders. The lesion in P4-6 is an example of bullous impetigo but certainly pemphigus foliaceus and even subcorneal pustular dermatosis should be considered in the differential diagnosis. In contrast to the findings in staphylococcal scalded skin syndrome in which special stains are characteristically negative, in lesions of bullous impetigo, it is often possible to find colonies of cocci.

S2C10P4-7 a & b (pustulosis palmaris et plantaris): The character of the keratin layer would suggest that the biopsy is from an acral site. There is a rounded defect in the epidermis which contains a loose infiltrate of neutrophils; the lesion qualifies as an intra-epidermal pustule. There is a plate of parakeratotic debris between the keratin layer and the viable epidermis. At the margin of the pustule in P4-7b (to the right), there are small, lytic defects among keratinocytes and these defects contain neutrophils. In this site, the patterns are spongioform and pustular.

In P4-7, a variation in the pattern of spongioform pustule is represented. The lesion has a well-defined, single defect containing loose infiltrates of neutrophils. Only in spotty areas at the margin of this defect is the tell-tale marker of a spongioform pustule represented. On the basis of this finding, it is possible to extend the histologic pattern of psoriasiform disorders to include the clinical disorder, pustulosis palmaris et plantaris. Perhaps the nature of the superficial unit of the epidermis is different in acral areas. With the distinctive forms of keratinization in acral locations, the superficial unit may be less susceptible to the phenomena which lead to the formation of a classic spongioform pustule.

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