Microfilariae in cytology smears: real culprits or trapped accidentally by needles? A study of 10 cases

Role of fine needle aspiration cytology in diagnosing filarial arm cysts

Filariasis is prevalent in tropical and subtropical areas and is endemic in regions of India. Lymphatic filariasis in India is caused mainly by two species of nematodes: Wuchereria bancrofti and Brugia malayi, which invade the human lymphatic system. We report two cases of superficial cystic lesions of the upper limb revealed on fine needle aspiration (FNA) to be clinically unsuspected filariasis. Despite similar aetiologies, both cases revealed variations in aspirate nature, smear morphology and peripheral blood findings. FNA provides definitive diagnosis and is an important tool for diagnosing soft tissue swellings owing to filariasis.

Standard karyotyping concentrates microfilaria and can be a valid concentrating technique for their detection

During karyotype preparation from the bone marrow aspirates of 209 haematological malignancy cases, microfilaria were detected in four samples, whereas routine marrow and peripheral blood smears of these four cases did not show any parasite. The patients were recalled, and their peripheral blood was processed by karyotyping and standard concentration techniques. Karyotype preparation from peripheral blood was performed with and without addition of colchicine. When the blood was processed for karyotyping with colchicine, microfilaria were detected in the peripheral blood of all four patients. In samples without added colchicine, no parasite was observed. The same samples were processed by Knott's concentration technique, which showed microfilariae only in one of the four patients. Routine thick and thin smears of these patients showed no parasite. It seems that the standard karyotype preparation technique with colchicine concentrates the microfilariae in samples where parasite load is small and not demonstrable with standard techniques. Serological tests are available for W. bancrofti and costly, whereas no regular serodiagnosis is available for B. malayi. In a country like India, both parasites are endemic and patients are treated on clinical suspicion when parasitaemia could be low. Low parasitaemia is common because of repeated infection and partial immunity. In such circumstances, a cost-effective concentration technique like this may be useful.

Cytological diagnosis of filarial infection in an endemic area where screening and prophylaxis is in place

OBJECTIVE

Filariasis has a worldwide distribution. However, the disease is often overlooked or misdiagnosed because of its unusual presentations and there may be false-negative results in endemic areas. This study was carried out to assess the role of cytology in the demonstration of filarial parasites in an area where screening and prophylaxis are in place.

METHODS

This study was carried out in Wardha district in central India, which is endemic for filarial infection. A total of 9182 smears of cases undergoing cytological evaluation were routinely screened at the time of reporting for the presence of adult filarial worm, microfilarial larvae or their fertilized and unfertilized eggs, irrespective of their original clinical diagnosis.

RESULTS

Microfilariae were found incidentally in fine needle aspiration (FNA) smears of patients presenting with other clinical conditions. Smears of seven cases were found to be positive for microfilaria. Four cases presented with subcutaneous nodules in the upper arm, two cases were seen incidentally in axillary lymph node aspirates and microfilariae were found in the pleural fluid in one case. Another case was suspected to have breast cancer, but aspirates from the axillary area showed lymphatic obstruction considered to be due to filariasis.

CONCLUSION

FNA cytology is an inexpensive, simple and easy procedure for detecting microfilariae. Detection of microfilariae may not be common even in endemic areas as screening and prophylaxis is routinely performed, and patients may show atypical presentations such as subcutaneous nodules. We believe that careful screening of FNAs, especially those from subcutaneous swellings, as well as serous fluids, is very important in a filariasis-endemic zone.