Sweet's syndrome
Early
| Small nodular infiltrates of neutrophils and nuclear "dust" of neutrophils around vessels within the upper half of the dermis |
| Slight edema of the papillary dermis |
| Lymphocytes around venules |
Fully developed
| Large nodular infiltrates of neutrophils and nuclear "dust" of neutrophils in "top-heavy" fashion within the dermis, sometimes throughout it; immature mononuclear neutrophils (promyelocytes) may be present and predominant |
| Lymphocytes and eosinophils sometimes within nodules of neutrophils; some lymphocytes around around venules |
| Marked edema of the papillary dermis verging on subepidermal vesiculation in some instances; intraepidermal vesicles also possible |
| Focal degeneration of collagen within collections of neutrophils |
| Neutrophils sometimes scattered within the epidermis; pustules possible |
Late
| All the findings described for fully developed lesions, but without neutrophils in the epidermis and without edema in the papillary dermis |