Incidental Detection of Microfilaria in Fine Needle Aspiration Cytology- A Report of Three Cases

Abstract

Lymphatic filariasis, a major global health problem, is a mosquito-borne parasitic disease, encountered mainly in the tropics and subtropics. The disease is endemic in Southeast Asia, including the Indian subcontinent. It is transmitted by mosquitoes and is caused by the filarial nematodes Wuchereria bancrofti, Brugia malayi and Brugia timori. Usually, the infected person remains asymptomatic for years together and later manifests with features and consequences of lymphatic obstruction. The adult forms of the nematodes live in human lymphatics, whereas the infective larval form, the microfilaria circulates in the peripheral blood. The nocturnal periodicity of the microfilaria makes it challenging to detect in routine peripheral blood smear examinations. Also, it is quite unusual to find the microfilaria in fine needle aspirations. However, rare cases have been reported in certain unusual sites, like lymph nodes, cutaneous swellings, bone marrow, bronchial aspirate, breast, nipple discharge, cervicovaginal smears, pleural, pericardial, ascitic fluids, ovarian cyst fluids or even thyroid. Very few cases of microfilaria in thyroid aspirates have been reported till date. Also, it is unusual to find microfilaria in lymph node and breast aspirations. Herewith, three cases of microfilariasis are reported at three uncommon sites like thyroid, lymph node and breast.