Unicentric Castleman Disease Presenting as an Isolated Submandibular Mass: Diagnostic Challenges for the Otolaryngologist

Background: Castleman disease (CD) is a rare lymphoproliferative disorder characterized by abnormal lymph node hyperplasia. Although the mediastinum represents the most frequent site of involvement, cervical localization is uncommon and may present a diagnostic challenge due to nonspecific clinical and radiological findings. Case Presentation: We report the case of a 44-year-old woman who presented with a progressively enlarging painless mass in the left submandibular region evolving over two months. Physical examination revealed a firm, mobile lymph node measuring approximately 2 cm without associated systemic symptoms. Laboratory investigations were unremarkable. Cervical computed tomography demonstrated a well-defined lymph node enlargement at level IB. The patient underwent complete surgical excision of the lesion. Histopathological examination revealed regressed germinal centers with hyalinized vessels and concentric mantle zones (“onion-skin” appearance), consistent with the hyaline-vascular subtype of unicentric Castleman disease. Postoperative positron emission tomography showed no additional sites of disease. Discussion: Cervical unicentric Castleman disease is rare and often mimics other causes of cervical lymphadenopathy, including lymphoma, metastatic lymph nodes, or benign inflammatory conditions. Because imaging and cytology are frequently inconclusive, definitive diagnosis relies on histopathological evaluation following surgical excision. Conclusion: This case highlights the importance of considering Castleman disease in the differential diagnosis of isolated cervical lymphadenopathy. Complete surgical excision remains both the diagnostic and curative treatment for unicentric forms of the disease.