Table 9 Histologic differential diagnosis of Sweet's syndrome

Bowel (intestinal) bypass syndrome

History of jejunal-ileal bypass surgery for morbid obesity

Erythema elevatum diutinum

Erythematous asymptomatic plaques often located on the dorsal hands and elbows; younger lesions have microscopic features of leukocytoclastic vasculitis, whereas older lesions have dermal fibrosis and mucin

Granuloma faciale

Yellow to red to brown indurated asymptomatic facial plaques; there is a grenz zone of normal papillary dermis beneath which there is a dense diffuse inflammatory infiltrate of predominantly neutrophils (with microscopic features of leukocytoclastic vasculitis) and frequently numerous eosinophils

Halogenoderma

Neutrophilic dermal infiltrate with necrosis and pseudoepitheliomatous hyperplasia with intraepidermal abscesses; history of ingestion of bromides (leg lesions), iodides (facial lesions), or topical fluoride gel to teeth during tumor radiation therapy to face

Leukemia cutis

Dermal infiltrate consists of immature neutrophils

Leukocytoclastic vasculitis

Vessel wall destruction – extravasated erythrocytes, fibrinoid necrosis of vessel walls, karyorrhexis, and neutrophils in the vessel wall

Lobular neutrophilic panniculitides

In addition to subcutaneous Sweet's syndrome, these include alpha 1-antitrypsin deficiency syndrome, factitial panniculitis (secondary to the presence of iatrogenic or self-induced foreign bodies), infectious panniculitis (secondary to either a bacterial, fungal, mycobacterial, or protozoan organism), pancreatic panniculitis, rheumatoid arthritis-associated panniculitis

Neutrophilic eccrine hidradenitis

Neutrophils around eccrine glands, often in patients with acute myelogenous leukemia receiving induction chemotherapy

Pyoderma gangrenosum

Painful ulcer with overhanging, undermined violaceous edges

Rheumatoid neutrophilic dermatitis

History of rheumatoid arthritis, nodules, and plaques

Sweet's syndrome

Acute onset, fever, neutrophilia, and painful plaques