Langerhans cell histiocytosis in lymph nodes. Cytomorphologic diagnosis and pitfalls

OBJECTIVE: To delineate the cytomorphology of Langerhans cell histiocytosis (LCH) in lymph nodes. STUDY DESIGN: Nine histologically documented LCH cases with a prior lymph node aspirate and five more cases in which a cytologic diagnosis of LCH was rendered in a background of corroborative clinical and radiologic findings were included in a retrospective study over a 12-year period (January 1988-January 2000). Papanicolaou- and May-Grünwald-Geimsa-stained smears were reviewed by two independent observers. Staining for S-100 protein was available in four cases. RESULTS: Nine cases had multisystem involvement, while in five cases only lymph nodes were involved. The ages ranged from 5 months to 27 years, with 11 males and 3 females. An initial cytologic diagnosis of LCH had been rendered in six, suspected in four and missed in four. On review, all were reclassified as LCH except two cases, which were still thought to be reactive and necrotizing lymphadenitis. The pathognomic feature of LCH, the "LCH cell," was identified in 12 of 14 cases along with varying numbers of eosinophils, polymorphs and lymphocytes. Giant cells were seen in six cases, and plasma cells were rarely seen. CONCLUSION: Lymph node involvement by LCH can be identified by fine needle aspiration in 85% of cases. The presence of the LCH cell is a must. The differentials to be considered are dermatopathic lymphadenitis, sinus histiocytosis with massive lymph-adenopathy, Hodgkin's lymphoma and malignant histiocytosis.