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

Background: 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. Objectives: We aimed to analyse clinicopathological characteristics, treatment, and outcomes of patients with Sweet syndrome according to concurrent malignancy. Materials & Methods: We retrospectively reviewed patients with Sweet syndrome at the Department of Dermatology from January 2001 to August 2021. Results: 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. Conclusion: 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.