Castleman's disease is a rare pathology, poorly understood. It is considered as a lymphoproliferative disorder, described for the first time in 1954, which may be confused with other causes of lymphadenopathy. We report in this paper the case of a young women presenting with left latero-cervical lymphadenopathy. All the investigations were negative except a large high-vascularized level II cervical lymphadenopathy. We performed a cervicotomy. The extemporaneous histological exam was non-contributive. We decided to perform a complete level II and III left cervical lymphadenectomy. The diagnosis of unicentric Castleman's disease was confirmed based on the final histological study of the specimen, and the absence of other cervical and extra-cervical lymphadenopathy. The patient is free of recurrence at the time of reporting this article.