Sweet syndrome in patients with and without malignancy: a retrospective study of 66 cases from a tertiary care centre

Sweet syndrome is a neutrophilic dermatosis that may be associated with malignancy, particularly haematological malignancy. Considering its rarity, the clinical characteristics of Sweet syndrome are still unclear. We aimed to analyse clinicopathological characteristics, treatment, and outcomes of patients with Sweet syndrome according to concurrent malignancy. We retrospectively reviewed patients with Sweet syndrome at the Department of Dermatology from January 2001 to August 2021. We identified 66 patients (median age: 58 years old; 57.6% male) with Sweet syndrome: 24.2% with the classic form, 36.3% with the malignancy-associated form, and 15.1% with the drug-induced form. Idiopathic Sweet syndrome was most common in the non-malignancy group (18.1%). Leukopenia (p = 0.008), anaemia (p = 0.004), and thrombocytopenia (p = 0.013) were significantly associated with malignancy. No significant difference in histopathology was identified between patients with and without haematological malignancy. Systemic corticosteroids were the most commonly used therapy (n=44, 66.6%). Relapse of Sweet syndrome was more prevalent in the malignancy group. Patients with Sweet syndrome who have laboratory evidence of leukopenia, anaemia and thrombocytopenia should be investigated for malignancy. Sweet syndrome often occurs as a paraneoplastic feature.