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

@