BACKGROUND: Filariasis is a major public health problem in tropical co
untries, including India. Despite this high incidence, it is unusual t
o find microfilariae in fine needle aspiration cytology (FNAC) smears
and body fluids. Six cases of filariasis diagnosed by FNAC are reporte
d. CASES: In case 1, a thyroid aspirate from a 23-year-old female show
ed a microfilaria with colloid and thyroid follicular cells. In case 2
, pericardial fluid from a 50-year-old male with breathlessness and ch
est pain showed clusters of malignant cells and many microfilariae. In
case 3, a bronchial aspirate from a 55-year-old male with fever and c
hest pain showed aggregates of acute inflammatory cells and a microfil
aria. Cases 4 and 5 were lymph node aspirates from a 29-year-old male
and 3-year-old female. Both smears showed microfilariae in a backgroun
d of reactive lymphoid cells. In case 6, FNAC from a 21-year-old femal
e with a cystic swelling in the breast showed clusters of microfilaria
e, lymphocytes and granular debris. CONCLUSION: In three of the six ca
ses microfilariae were the cause of symptoms, whereas in the other thr
ee cases, microfilariae were associated with other diseases, including
malignancy. Thus, careful screening of FNAC smears might be helpful i
n detecting microfilariae, even in asymptomatic patients.