We report on a 15-year-old female patient with a slow-growing, mildly painful swelling on her neck, without any signs of inflammation or any general symptoms. Sonographic findings included two enlarged lymph nodes with hilar markings evident. Based on the histology, Castleman's disease of the hyaline vascular type was ultimately diagnosed. The differential diagnosis of the swelling on the neck is described along with the clinical, diagnostic, pathogenic and therapeutic aspects of Castleman's disease. Castleman's disease is a rare differential diagnosis of non-infectious cervical lymphadenopathy. Unicentric Castleman's is treated by surgical resection. In patients with contraindications, radiotherapy should be discussed as an alternative. Multicentric forms manifest as systemic diseases with poor prognosis and must be managed by an interdisciplinary team.