Unicentric Castleman Disease in a Pediatric Patient: A Case Report and Review of Pathological and Therapeutic Insights

Castleman disease is a rare lymphoproliferative disorder classified into unicentric (UCD) and multicentric (MCD) forms. UCD typically presents as localized lymph node enlargement, often asymptomatic, whereas MCD is characterized by systemic symptoms resulting from abnormal interleukin-6 overproduction. The hyaline-vascular variant (HV-UCD) is the most common subtype, characterized by atrophic germinal centers, concentric mantle zone hyperplasia, and marked vascular proliferation. This variant is primarily observed in adults, with pediatric cases being rare. Diagnosis relies on a combination of clinical presentation, imaging findings, histopathological examination, and immunohistochemistry to differentiate UCD from other lymphoproliferative disorders and infectious lymphadenopathies. We report the case of an 8-year-old girl who presented with a painless, mobile swelling in the right supraclavicular region. Clinical examination revealed isolated lymphadenopathy without hepatosplenomegaly or systemic symptoms. A thoracoabdominopelvic computed tomography (CT) scan identified multiple infra-centimetric lymph nodes in both supradiaphragmatic and subdiaphragmatic regions, with no evidence of distant metastases. Excisional biopsy of the supraclavicular lymph node showed atypical follicular hyperplasia with an "onion-skin" pattern due to concentric layering of mantle zone cells, follicular dendritic cell hyperplasia, and hyalinized capillaries. Immunohistochemical analysis revealed CD20 positivity in lymphoid nodules, CD3 staining of interfollicular lymphocytes, CD21 highlighting follicular dendritic cells, and CD138-positive plasmacytic aggregates. Negative results for HHV-8 and HIV ruled out viral-induced lymphadenopathy. Initial corticosteroid therapy led to partial improvement in systemic symptoms, followed by complete surgical excision of the affected lymph node. The postoperative course was uneventful, with progressive improvement and no recurrence or complications during follow-up. This case emphasizes the importance of considering HV-UCD in pediatric patients presenting with isolated lymphadenopathy, as early surgical intervention is crucial for long-term remission. Long-term follow-up remains essential due to the potential risk of recurrence and secondary malignancies.