|Year : 2016 | Volume
| Issue : 2 | Page : 86-88
Microfilaria in fine needle aspirate of thyroid nodule
Richa Bhartiya, Mahasweta Mallik, Nawanita Kumari, Manish Kumar
Department of Pathology, Patna Medical College and Hospital, Patna, Bihar, India
|Date of Web Publication||1-Jun-2016|
Dr. Richa Bhartiya
C/o Shri Vinay Kumar Shrivastava, Bungalow No. 882, Railway Officers' Colony, Danapur, Khagaul - 801 105, Patna, Bihar
Source of Support: None, Conflict of Interest: None
Filariasis is a major public health problem in tropical countries including India. About 90% of cases of lymphatic filariasis are caused by infection with Wuchereria bancrofti and rest by Brugia malayi in Southeast Asia. Filariasis is transmitted by the bite of Culex mosquitoes. The diagnosis of it is conventionally made by demonstrating microfilaria in the peripheral blood smear. Microfilaria have been incidentally detected in fine needle aspiration cytology smears from various sites. However, the presence of filarial worm in thyroid aspirate is unusual. We report a case in which aspiration cytology revealed presence of microfilaria in thyroid nodule.
Keywords: Elephantiasis, endemic, filariasis, lymphadenitis, lymphatics, malignant
|How to cite this article:|
Bhartiya R, Mallik M, Kumari N, Kumar M. Microfilaria in fine needle aspirate of thyroid nodule. Thyroid Res Pract 2016;13:86-8
| Introduction|| |
Filariasis is a global problem. It is a major social and economic scourge in the tropics and subtropics of Africa, Asia, Western Pacific, and parts of the Americas, affecting over 73 countries. More than 1.4 billion people live in areas where there is a risk of infection, of whom 120 million are infected and in need of treatment, including 40 million people with overt disease. The disease is endemic all over India with heavily infected areas are found in Uttar Pradesh, Bihar, Jharkhand, Andhra Pradesh, Odisha, Tamil Nadu, Kerala, and Gujarat. An estimated 600 million people are at a risk of lymphatic filariasis in India. Filariasis in India is caused by two closely related nematode worms namely Waucheria bancrofti and Brugia malayi.
| Case Report|| |
A 30-year-old female presented with anterior neck swelling since 5 months. On clinical examination, her general condition was good. On local examination, 3 cm × 3 cm, soft to firm, nontender swelling which moved with deglutition was noted on the right lobe of her thyroid gland. Laboratory and radiological work-up revealed normal hemoglobin of 12.5 g/dl (normal – 13–17 g/dl). Total leukocyte count was high 12,800/µl and the differential leukocyte count showed eosinophil count 12%. Absolute eosinophil count was 2750/µl. Thyroid function test was within normal limits. Ultrasonography findings were suggestive of neoplastic lesion of thyroid. Later, patient was subjected to fine needle aspiration of thyroid swelling. Fine needle aspiration cytology (FNAC) was performed by using 24 gauge needle and 10 ml syringe. Smears were stained with Giemsa and Papanicolaou stain. The smears revealed microfilaria, along with few follicular cells, lymphocytes, macrophages, and colloid in the background and in high power view these microfilaria were identified as those of W. bancrofti by the presence of a hyline sheath, the length of the cephalic space and the presence of somatic cells (nuclei). The somatic cells appeared as granules that extended from head to the tail, the tail-tip was free of nuclei [Figure 1] and [Figure 2] making the diagnosis of microfilaria of W. bancrofti in thyroid. Subsequently, night samples of peripheral blood smear were obtained, which was negative for microfilaria. The patient received combination therapy of diethyl carbamazine citrate (DEC), amoxicillin clavulinic acid, albendazole, and responded well.
|Figure 1: Microfilaria of Waucheria bancrofti with a few follicular cells, lymphocytes, and colloid material in the background (Giemsa, ×400)|
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|Figure 2: Microfilaria of Waucheria bancrofti with lymphocytes and colloid material in the background (Giemsa, ×1000)|
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| Discussion|| |
Medical literature documents filariasis back to 600 BC by Sustruta who recognized the clinical manifestation of elephantiasis and referred it as elephantiasis arabicum. Historically, the larval forms of the parasite were first found by Demarquay in 1863 in the hydrocele fluid of man. Later, Waucheria in 1866 found them in the chylous urine and Lewis in 1872 found them in the human blood. Bancrofti in 1876 found the adult females, hence specific name was given after the discoverer. W. bancrofti passes its life-cycle in two hosts; man and mosquito, the definitive host is man in whose lymphatic system the adult worms are harbored. Most frequently involved lymphatics are those of lower limbs, retroperitoneal tissue, spermatic cord, epididymis, and mammary gland., Microfilaria are discharged which find their way into blood stream. There are eight species of microfilaria of which W. bancrofti, B. malayi and Brugia timori are responsible for lymphatic filariasis. Of these, the first two are common in India microfilaria in India display a nocturnal periodicity that is they appear in large numbers in night and retreat from bloodstream during the day. It is difficult to find microfilaria in blood and FNAC aspirate despite the high incidence of it in the endemic area. A majority of infected individuals in filarial endemic communities are asymptomatic. The disease manifestations range from none to both acute and chronic manifestations such as lymphangitis, lymphadenitis, elephantiasis of genitals, legs, and arms. Diagnosis of filariasis is usually made by demonstration of microfilaria in peripheral blood or skin and detection of filarial antigen and antibody. Adult worms can be detected in lymphatics, subcutaneous tissue, peritoneal and pleural cavities, heart, brain, scrotum, and breast. There are various reports stating the presence of microfilaria using aspiration cytology in various sites such as spermatic cord, epididymis, testis, and retroperitoneum. The present case is rare manifestation of filarial infection that is infrequently seen in thyroid. Despite the high incidence of filariasis, microfilaria in FNAC of thyroid is not a common finding. The present case was amicrofilaremia as microfilaria was not demonstrated in peripheral blood smear of patient which itself rules out the possible contamination of blood. According to some authors, the presence of microfilaria in thyroid aspirate can be explained due to lodging of the parasite in the thyroid microvasculature and subsequent rupture., In case of filariasis, the host tissue immune response is variable ranging from only minimal reaction to dense inflammatory cell infilteration comprising, especially of eosinophils. The diagnosis of filariasis is solely made on the demonstration of adult worm and microfilaria. In our case, microfilaria was found in cytology aspirate of thyroid nodule whereas it was not detected in peripheral blood smear, which is in accordance with the report by Gangopadhyay et al., and a similar observation was also noted by Rekhiand Kane  patient responded well to the DEC therapy.
| Conclusion|| |
Thus an accurate and prompt diagnosis can be easily made by FNAC, which possibly helped in obviating surgery in such cases which can be treated with drugs. In countries such as India where lymphatic filariasis is endemic, it should be considered in the differential diagnosis. Careful screening of cytology smears can help in detecting microfilaria even in asymptiomatic patients.
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[Figure 1], [Figure 2]