S5C18aP12aGraftvsHost



S5C18aP12a-1: In this graft vs host reaction, the superficial unit is hyperplastic. The basal layer focally is interrupted. Focally, palisaded cells are represented in “basal cell” patterns. In other foci, hypertrophied keratinocytes extend to the basement membrane zone and the basement membrane is slightly coarsened; it is more brightly acidophilic. Necrotic keratinocytes are present in the intermediate zone of the epidermis (between the superficial layer and a hyperplastic basal layer [blue arrows]). The lesion is cell-poor in regard to lymphoid infiltrates. Lymphocytes and histiocytes are present among keratinocytes in the region of the necrotic cells (generally over the areas showing partial preservation of the basal layer). The dermis shows hyperplasia of fibrocytes. Vessels are ectatic. The lesion has l upus erythematosus-like qualities and the upper migration of necrotic cells is reminiscent of the transport of necrotic cells to the surface as seen in lesions of subacute lupus erythematosus.

S5C18aP12a-2: At higher magnification, blue arrows point to a slightly accentuated basement membrane. Above the area identified with blue arrows, basal keratinocytes have lost their “basal cell” qualities. The cells are individually hypertrophied; they have acidophilic, rather than basophilic, cytoplasm. Nuclei are enlarged; they have prominent nucleoli. A small island of more characteristic basal cells is represented to the right. Lymphocytes and histiocytes have clustered in the basal unit of the epidermis near the dead and dying keratinocytes (apoptotic patterns; satellite cell necrosis ). To the left above the basement membrane, cytopathic changes are represented. Some of the cells show cytoplasmic pallor and some show cytoplasmic acidophilia (dyskeratosis). Some of the patterns are erythema multiforme-like.

S5C18aP12a-3: Apoptosis with patterns of satellite cell necrosis.

	S5C18aP12a-4: The focal lytic defects at the tips of small, thin, dermal papillae might be characterized as an erythema multiforme-like quality. In the areas outlined by red arrows, basal keratinocytes are arranged in whorls.

S5C18aP12a-5: Satellite cell necrosis. Some of the cells in apposition to the necrotic keratinocytes appear to be dendritic histiocytes. One cell, whose nucleus has the configuration of a “cocked” hat, is interpreted as a transformed lymphoid cell.

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