Histopathology of a skin biopsy from a tender, erythematous plaque in a patient with Sweet's syndrome would show:

• A Leukocytoclastic vasculitis with fibrinoid necrosis of vessel walls
• B Lichenoid interface dermatitis with colloid bodies
• C Palisading granulomas surrounding necrobiotic collagen
• D Dense dermal neutrophilic infiltrate with nuclear dust but WITHOUT vasculitis ✓

Explanation

Sweet's syndrome is a neutrophilic dermatosis; the defining histopathological feature is a dense dermal infiltrate of mature neutrophils with prominent nuclear fragmentation (karyorrhexis/nuclear dust) WITHOUT evidence of vasculitis — this distinguishes it from leukocytoclastic vasculitis where fibrinoid necrosis of vessel walls is the hallmark. Oedema of the papillary dermis is also characteristically prominent. The absence of vasculitis is critical to the diagnosis and explains why it is classified as a 'neutrophilic' rather than 'vasculitic' dermatosis.

Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.