The aim of this paper is to report our clinical experience of Sweet's syndrome, a severe dermatological disease which may be extremely important to recognize for the early diagnosis of a neoplastic disorder. Eleven patients affected by Sweet's syndrome, treated at the Department of Dermatology, University of Ferrara, Ferrara, Italy, during 1998 to 2004, were evaluated. A retrospective analysis was performed. Data on age, sex distribution, clinical data, histopathological and immunohistochemical findings and therapy were collected. We observed one patient with idiopathic form, 5 patients affected by the para-inflammatory variant and 5 para-neoplastic cases (with haemoproliferative diseases). The cases with the para-inflammatory form were affected by minor infectious manifestations. Prolonged follow-up is necessary to verify that a case of idiopathic variant is not really a paraneoplastic form. Based on immunohistochemical analysis, we cannot exclude that true histiocytes, immunoreactive for CD68/PGM, infiltrate the dermis in Sweet's syndrome lesions.