S7C7P4-3: In this lesion of incontinentia pigmenti, intra-cellular edema and ballooning degeneration are features; the result is a reticulated vesicle.

S7C7P4-4: A portion of a subepidermal bullous lesion is represented. The detached epidermis is pale; it is necrotic. The papillary dermis is widened. There are mininal infiltrates of lymphoid cells in the dermis. The lesion is cell-poor (toxic epidermal necrosis).

S7C7P4-5: The roof of the vesicle is necrotic; it is irregularly pigmented. The basal layer of the roof of the bulla can not be defined. The keratin layer is relatively normal (the insult to the epidermis was acute). The papillary dermis is edematous and cell-poor. Epithelium has partially regenerated along the floor of this sub-epidermal defect. On the left, the epidermis shows hyperplasia of the basal unit (lavender cytoplasm of keratinocytes is evidence of regeneration). The patterns resemble those of toxic epidermal necrolysis but, clinically, the lesions were bullous and localized. The patient had been told she had a herpes infection, but there was little actual documentation of such an event. The patient was taking many drugs. Although, it was assumed that this represented post-herpes erythema multiforme, this cell-poor pattern is more characteristic of a drug reaction; post-herpes erythema multiforme generally is a reaction that is richer in cells (assuming that the immune mechanism is intact).

S7C7P4-6: On the left, epidermis has partially regenerated along the floor of the bulla. The necrotic epidermis shows scattered clumps of melanin. The cytoplasm of the regenerating epidermis along the floor of the defect is lavender.

S7C7P4-7: In the area outlined by green arrows, pigmented, dyskeratotic cells (apoptotic cells) are clustered. This clustering of necrotic cells is a common feature in a lichenoid reaction of the erythema multiforme-type. Both herpes virus infections and toxic epidermal necrolysis are expressed in erythema multiforme-like patterns.

S7C7P4-8: At the margin of the bulla (i.e., the defect to the right), the epidermis shows hyperplasia of the basal unit with increased cytoplasmic basophilia (a feature of regenerating epithelium). Scattered pigmented, necrotic keratinocytes are present at the interface between viable epidermis and the keratin layer. At the bottom of the field and slightly to the right of center, the lichenoid reaction involves a sweat duct.