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Year : 2008  |  Volume : 51  |  Issue : 1  |  Page : 94-96
Microfilaria in thyroid gland nodule

Department of Patholgy, Lady Hardinge Medical College, New Delhi, India

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Presence of microfilaria in the thyroid gland is a rare finding. Filariasis is a common public health problem in the Indian sub-continent. Most of the cases of microfilaria in thyroid gland reported in the literature are associated with goiter and thyroid neoplasms. Here, we present a rare case that showed microfilaria on fine needle aspiration cytology of solitary thyroid nodule.

Keywords: Microfilaria, thyroid gland, fine needle aspiration

How to cite this article:
Chowdhary M, Langer S, Aggarwal M, Agarwal C. Microfilaria in thyroid gland nodule. Indian J Pathol Microbiol 2008;51:94-6

How to cite this URL:
Chowdhary M, Langer S, Aggarwal M, Agarwal C. Microfilaria in thyroid gland nodule. Indian J Pathol Microbiol [serial online] 2008 [cited 2023 Sep 27];51:94-6. Available from:

   Introduction Top

Filariasis is a common public health problem in the Southeast Asia. There are approximately 60 million people infected in the region and approximately 31 million people have the clinical manifestation of this disease. Filariasis in India is caused by two closely related nematode worms - W. bancrofti and B. malayi . [1] The disease mainly involves the lymphatic system of the body. The most frequently involved lymphatics are those of lower limbs, retroperitoneal tissues, spermatic cord, epididymis and mammary gland. [2],[3]

Although the incidence is high in the Indian sub-continent, yet it is unusual to find microfilaria on fine needle aspiration cytology. We report an interesting case of microfilaria in solitary thyroid nodule of a euthyroid female patient.

   Case History Top

A 24-year-old female presented in the ENT outpatient department with a solitary nodule on the left side of thyroid with a duration of 8 months. The size of the nodule was 4 cm x 3 cm and it was soft to firm, non-tender and moved with deglutition. The peripheral blood showed a total leucocyte count of 65000/l and the differential leukocyte count (DLC) showed 15% eosinophils. The absolute eosinophil count was 8750/l. ESR was 22 mm in the first hour. Thyroid serology was normal. A clinical diagnosis of a neoplastic lesion of the thyroid was made, and patient was sent for the aspiration of the thyroid nodule. Fine needle aspiration cytology was performed using 10 ml disposable syringe and a 23-gauge needle. Papanicolaou and Giemsa stained smears revealed microfilariae of Wuchereria bancrofti along with few clusters of thyroid follicular cells, pseudogiant cells, foam cells and scanty thin colloid. Higher magnification revealed microfilariae with a clear space at the cephalic and caudal ends [Figure - 1]. A diagnosis of microfilariae of W. bancrofti in thyroid was made. Patient was advised diethyl carbamazine (DEC) and chlorpheniramine maleate for 21 days. This cycle was repeated after a gap period of 21 days. Patient responded to the treatment and the nodule disappeared by the end of three months.

   Discussion Top

Lymphatic filariasis is a common public health problem of tropical and subtropical countries including parts of Latin America, Sub-Saharan Africa and Southeast Asia. It is estimated that approximately 600 million people are living in areas endemic for lymphatic filariasis in Southeast Asia Region. There are approximately 60 million people infected in the region and approximately 31 million people have clinical manifestation of the disease. [1]

It is transmitted by Culex mosquito and is caused by two closely related nematodes Wuchereria Bancrofti and Brugia malayi that are responsible for 90% and 10% cases, respectively, of the 90 million infections worldwide. Adult worms live in the lymphatic vessels of the definitive host and microfilaria is released and circulated in the peripheral blood. Most frequently involved lymphatics are those of lower limbs, retroperitoneal tissue, spermatic cord, epididymis and mammary gland. [2],[3] Filariasis causes a spectrum of diseases including asymptomatic microfilaremia, acute lymphangitis and lymphadenitis, chronic lymphadenitis, edema of limbs and genitalia and tropical pulmonary eosinophilia. [4]

Despite a large number of people affected worldwide, it is quite unusual to find microfilaria in routine cytological smears. There have been reports of single or small number of cases of microfilaremia at various sites as lymphnode, breast lump, bone marrow, bronchial aspirate, nipple secretions, pleural and pericardial fluid, ovarian cyst fluid and cervicovaginal smears. [5],[6] Thyroid is another rare site from which microfilaria has been isolated. [2],[3],[5],[6],[7],[8],[9],[10] On the extensive review of literature, we could find only eight cases describing microfilaria in thyroid [Table - 1]. In most of these cases, microfilaria was seen as an incidental finding in one or the other primary thyroid lesion. The index case is unique that the patient presented with solitary thyroid nodule, which showed microfilaria on FNAC. Patient was clinically asymptomatic other than peripheral blood eosinophilia and there was no clinical, radiological or serological evidence of any other thyroid disease. The nodule subsided completely after treatment.

Kundu et al. have also described a similar case in a 38-year-old female who also presented with a solitary thyroid nodule, aspirate of which revealed microfilaria, few histiocytes and lymphocytes. [10] There was no other associated thyroid lesions and the nodule resolved after treatment with DEC.

It is well established that larval forms of W. Bancrofti and B. Malayi circulate in the body till they are picked by an intermediate host. Walter et al. suggested that microfilaria appears in the tissue fluid and exfoliated surface material due to lymphatic and vascular obstruction and subsequent extravasation. The finding of microfilaria in pericardial fluid, breast cyst fluid and bronchial aspirate may be explained in this way. However, the presence of microfilaria in thyroid aspirate cannot be explained in a similar manner. Some authors have suggested that presence of microfilaria in thyroid could be the result of lodging of the parasite in intrathyroid microvasculature and subsequent rupture. [6],[7] In the present case, the patient appears to be an asymptomatic carrier with larvae present in microvasculature of thyroid gland. A possible rupture of vessels may have led to hemorrhage and release of microfilaria in the thyroid and subsequent histiocytic reaction which led to development of a solitary thyroid nodule.

This case is interesting because clinically patient was suspected to have a neoplastic lesion, but the aspirate contained microfilaria. FNAC thus averted the invasive procedure of an open biopsy.

   References Top

1.Park K. Park's Textbook of Preventive and Social Medicine. 18 th ed. Jabalpur; p. 211-6.  Back to cited text no. 1    
2.Sodhani P, Nayar M. Microfilariae in a thyroid aspirate smear: An incidental finding. Acta cytol 1989;33:942-3.  Back to cited text no. 2    
3.Yenkeshwar PN, Kumbhalkar DT, Bobhate SK. Microfilariae in fine needle aspirate: A report of 22 cases. Indian J Pathol Microbiol 2006;49:365-9.  Back to cited text no. 3    
4.Mcadam AJ, Sharpe HA. Infectious diseases. Robbins and Cotran Pathologic Basis of Disease. In : Kumar V, Abbas AK, Fausto N, editors. 7 th ed. Philadelphia.  Back to cited text no. 4    
5.Pandit A, Prayag AS. Microfilaria in thyroid smear: An unusual finding. Acta Cytol 1993;37:845-6.  Back to cited text no. 5    
6.Varghese R, Raghuveer CV, Pai MR, Bansal R. Microfilariae in cytologic smears: A report of six cases. Acta Cytol 1996;40:299-301.  Back to cited text no. 6    
7.Mehrotra R, Lahiri VL, Hazara DK. Microfilariae identified in FNA of a thyroid nodule. Diagnost Cytopathol 1997;16:149-50.  Back to cited text no. 7    
8.Mohanty SK, Patnaik S, Dey P. Microfilaria in thyroid aspirate. Diagn Cytopathol 2002;26:197-8.  Back to cited text no. 8    
9.Kar DK, Agarwal G, Krishnani N, Mishra SK. Microfilaria in thyroid: A histopathological encounter. Thyroid 2001;11:401.  Back to cited text no. 9    
10.Kundu AK, Giri A, Ghosh G, Saha SR. Microfilaria in a thyroid nodule that resolved on treatment. Trop Doct 2002;32:248.  Back to cited text no. 10    

Correspondence Address:
Chetna Agarwal
A-86, Sector 27, Noida - 201 301, UP
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0377-4929.40415

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  [Table - 1]

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