Fine needle aspiration cytology of Langerhans cell histiocytosis involving the thyroid. A case report.

We present an unusual case of Langerhans cell histiocytosis (LCH) involving the thyroid gland initially diagnosed by fine needle aspiration biopsy in a 16-year-old boy. The cytologic findings in LCH involving the thyroid include high cellularity, isolated Langerhans cells with prominent nuclear grooves, multinucleate Langerhans cells, eosinophils, lymphocytes and rare benign follicular cells. Confirmation of LCH was obtained by core biopsy, positive S-100 protein immunohistochemical staining and the demonstration of Birbeck granules on electron microscopy. We present the complete clinicopathologic features of this case with a review of the literature and discussion of the differential diagnosis.