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

BACKGROUND: Langerhans cell histiocytosis (LCH) of the thyroid is a rare co ndition, and fine needle aspiration cytology (FNAC) of this entity has rare ly been described. CASE: FNAC was done on a 3-cm-diameter thyroid swelling in the left lower l obe of the thyroid gland. Smears showed a large number of lymphocytes, eosi nophils, thyroid follicular cells and discrete, large cells with prominent nuclear grooves. Mitotic activity was frequent. A cytologic diagnosis of LC H was offered. Subtotal thyroidectomy was performed, and the cytologic diag nosis was confirmed by histology. CONCLUSION: LCH of the thyroid has certain salient diagnostic features. The presence of histiocytes with prominent nuclear grooves, reactive lymphoid cells and eosinophils along with benign thyroid follicular cells should rai se the suspicion of this rare entity on FNAC smears of the thyroid.