Incidental detection of microfilariae in aspirates from Ewing's sarcoma of bone.

Microfilariae have been reported as coincidental findings with various neoplasms. We present a case in which microfilariae were encountered in fine-needle aspiration (FNA) smears from a 10-yr-old boy who presented with a lytic lesion in the diaphysis of the right tibial bone. Stained aspirates from the swelling were composed of a dispersed population of small round cells with scanty to vacuolated cytoplasm. Two sheathed microfilariae with several nuclei and cephalic and caudal clearing were identified. A diagnosis of Ewing's sarcoma with presence of microfilariae of Wuchereria bancrofti was made. The diagnosis of Ewing's sarcoma was confirmed on histopathology.