Fine-needle aspiration cytology of histiocytosis X: a case report.

The cytologic features of a case of histiocytosis X diagnosed by fine-needle aspiration biopsy of a right cervical lymph node in a 15-mo-old girl are reported. Characteristic reticuloendothelial cells with abundant cytoplasm and grooved nuclei were observed. Electron microscopy of the aspiration-derived specimen revealed Birbeck granules. The cytologic pattern and electron microscopic demonstration of Birbeck granules allowed definite diagnosis of lymph node involvement by histiocytosis X, negating the need for open biopsy. The cytologic differential diagnosis and current diagnostic criteria for histiocytosis X are discussed.