|Year : 2012 | Volume
| Issue : 1 | Page : 71-72
Cytological diagnosis of microfilariae in subcutaneous nodule
Narayanan K Panicker, Archana C Buch, Shruti Vimal, Arpana P Dharwadkar
Department of Pathology, D. Y. Patil Medical College and Research Centre, Pimpri, Pune, Maharashtra, India
|Date of Web Publication||20-Jun-2012|
D 1- 702 Nisarg Nirmiti, Pimple Saudagar, Pune - 27, Maharashtra
Source of Support: None, Conflict of Interest: None
Microfilariaemia presenting with subcutaneous nodule is rare. We report a case of a 22-year-old female patient who presented with a subcutaneous nodule on right forearm. Fine-needle aspiration cytology from the nodule showed many sheathed motile microfilaria on wet mount preparation during day time. Wuchereria loa loa is known to be associated with soft tissue swellings as reported earlier. Nocturnal motility and cytomorphological features differentiate Wuchereria bancrofti from Wuchereria loa loa.
Keywords: Filariasis, subcutaneous nodule, motile and fine-needle aspiration cytology
|How to cite this article:|
Panicker NK, Buch AC, Vimal S, Dharwadkar AP. Cytological diagnosis of microfilariae in subcutaneous nodule. Med J DY Patil Univ 2012;5:71-2
|How to cite this URL:|
Panicker NK, Buch AC, Vimal S, Dharwadkar AP. Cytological diagnosis of microfilariae in subcutaneous nodule. Med J DY Patil Univ [serial online] 2012 [cited 2020 Jan 19];5:71-2. Available from: http://www.mjdrdypu.org/text.asp?2012/5/1/71/97521
| Introduction|| |
Filariasis is a major public health problem in the tropics and subtropics and is commonly seen in countries like India, China, Indonesia, Africa, and the Far East. The life cycle of microfilariae is found in two hosts. Man is the definitive host and mosquito is an intermediate host. 
The different types of microfilaria found in humans are mainly divided under two broad categories, i.e. sheathed and unsheathed. Microfilaria bancrofti, Microfilaria malayi, and Microfilaria loa are the sheathed Microfilaria. Microfilariae perstans and Microfilariae ozzardi are the unsheathed variety.
Microfilaria have been detected on fine-needle aspiration cytology (FNAC) at different sites like breast, thyroid, lymph node, liver, lungs, and small number of cases have been reported in bone marrow and body fluids. A subcutaneous nodule though is a rare presentation. Wuchereria loa loa commonly presents as subcutaneous nodules and usually presents with day time motility in peripheral blood. ,,,,
A majority of infected individuals in filarial endemic communities are asymptomatic. Conventional mode of diagnosis of filariasis is by demonstration of microfilaria in peripheral blood smear. Despite the high incidence, it is infrequent to find microfilariae on FNAC smears and body fluids.
| Case Report|| |
A 22-year-old female presented with a painful, diffuse swelling on the left forearm measuring 3 cm in diameter since 1 month. There were no other significant complaints. Prior treatment consisted of topical application of some creams. Results of routine blood studies were normal. The patient was sent for FNAC for the presumptive diagnosis of the mass. Clear fluid was aspirated at first and on second attempt hemorrhagic material was aspirated.
Cytological examination revealed moderately cellular smears with lymphocytes, eosinophils, and multiple microfilaria on a hemorrhagic background [Figure 1]. Wet mount preparations were also done and they showed multiple motile sheathed microfilariae. They were sheathed, measured 300 μm to 7 μm and the column of nuclei in them extended up to the tail tip. The X-ray of the subcutaneous nodule did not show any calcification.
|Figure 1: FNAC smear showing microfi lariae of Wucheria Loa loa. The nucleus extends from the tip to the tail (Leishman stain 40×)|
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The patient was treated with diethylcarbamazine (Hetrazan) which is the drug of choice for the treatment of Loa loa filariasis for 21 days. After completion of treatment of the patient, the swelling subsided and the peripheral blood smear studies showed no microfilariae.
| Discussion|| |
Wuchereria bancrofti presenting as a subcutaneous nodule is a very rare presentation. The subcutaneous filariasis is mainly caused by W. loa loa, Onchocerca volvulus, and Mansonella streptococcus of which W. loa loa is found both in blood and subcutaneous nodule, while the other two are found in the skin.  Microfilariae have been identified cytologically at unusual sites such as thyroid, soft tissue, bone marrow, epididymis, lung, broncho-alveolar fluid, breast, gastric brushing, cervico-vaginal smears. and hydrocele fluid.  They have also been reported in association with various benign and malignant tumors such as hemangioma of liver, meningioma, intracranial hemangioblastoma, squamous cell, and undifferentiated carcinoma of the uterine cervix, pharyngeal carcinoma, lymphangiosarcoma, urinary bladder carcinoma, prepucial carcinoma, metastatic carcinoma, melanoma. and leukemia. 
In our study, needle aspiration from the subcutaneous nodule yielded clear aspirates and moderately cellular smears. They revealed many sheathed microfilaria. W. loa loa was confirmed by the presence of nuclei at both the cephalic end and tip of the tail and day time motility which differentiates it from W. bancrofti which shows the cephalic and the tail end free of nuclei and nocturnal motility. The cytomorphological features and micrometry study confirmed the microfilaria of W. loa loa.
The disease caused by the worm in man is known as loiasis. The incubation period on an average is about 3-4 yrs. The worm migrates to the various parts of the body through the subdermal connective tissues. During the migration, it causes edema of the subcutaneous tissue - "calabar swellings" or "fugitive swellings." Microfilarias are seldom found at this stage, but the history of calabar swellings associated with intense eosinophilia may help in the diagnosis. 
Alive and mobile adult worms and microfilaria do not excite any tissue reaction. Any restriction to their movement excites a variable but generally mild reaction. Dead and fixed worms and microfilaria excite severe reaction which may include eosinophilia, eosinophilic abscess, necrosis, and epithelioid granuloma. This is usually followed by fibrosis with or without calcification. These tissue reactions in the lymph node or in the lymphatics produce lymphedema. 
| Conclusion|| |
In endemic areas, filariasis should be considered as one of the differential diagnosis of a subcutaneous swelling. Careful screening of FNAC smears help in detecting microfilaria even in asymptomatic patients and thus plays a significant role in the recognition of the disease and institution of the specific treatment.
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