Langerhans cell histiocytosis diagnosed by FNAC of lymph nodes

Langerhans cell histiocytosis (LCH) is a rare clonal disorder of unknown etiology and characterized by the proliferation of dendritic cells. LCH most commonly involves the bone followed by the skin and the lymph nodes. Recently, only a few cases of LCH with predominant lymph node involvement have been diagnosed by fine-needle aspiration cytology (FNAC). A 2-year-old boy presented with generalized lymphadenopathy, fever, and cough. The patient had hepatosplenomegaly, anemia, and lytic lesions in the skull. FNAC from the largest submandibular lymph node showed features of LCH. The large cells of LCH showed positive immunostaining for S-100 protein on FNAC smears. Later, lymph node biopsy and immunohistochemistry against S-100 protein and CD1a confirmed the diagnosis of LCH. The patient was treated with chemotherapy and he is under regular follow-up. This case report highlights the importance of FNAC as a rapid and accurate investigation in the diagnosis of lymph node predominant LCH.