Hydatid cyst of the thyroid gland: report of three cases
- First Online:
- Cite this article as:
- Yilmaz, M., Akbulut, S., Sogutlu, G. et al. Surg Today (2013) 43: 937. doi:10.1007/s00595-012-0269-7
- 153 Views
Cystic Echinococcosis is a parasitic infestation that is distributed world-wide. It may be found in nearly any part of the body, most often in the liver and the lungs, but occasionally in other structures such as the thyroid gland. The present study reports three cases of hydatid cysts of the thyroid gland, in patient ranging from 18 to 25 years of age. Two patients had concomitant hydatid disease involving organs other than the thyroid gland (secondary disease), and one had, sole, involvement of the thyroid gland itself (primary disease). Moreover, an occult papillary thyroid carcinoma was detected incidentally in one case, involving the unilateral thyroid lobe as the hydatid cyst. While several surgical procedures including left lobectomy and isthmectomy were undertaken in one patient, two patients underwent total thyroidectomy. No disease recurrence was observed in any of the three patients during the postoperative follow-up period. No study reporting the concomitance of hydatid cyst and neoplasia of the thyroid gland has been previously published. This concomitance indicates the importance of the differential diagnosis of lesions characterized by calcifications in the thyroid gland, especially in endemic regions.
KeywordsHydatid cystUnusual locationThyroidDifferential diagnosis
Echinococcal disease, also known as hydatid disease, is common in societies in which agriculture and domesticated animals are common, and it continues to be a serious public health problem in many countries, including Turkey. Echinococcal disease is caused by infection from the metacestode stage of Echinococcus tapeworms of the family Taeniidae. Four species of Echinococcus cause infection in humans; E. granulosus and E. alveolaris are the most common, causing cystic echinococcosis and alveolar echinococcosis, respectively. The primary carriers are dogs and wolves, while the intermediate hosts are typically sheep, cattle, and deer. Humans, who are accidental hosts and do not play a role in the biological cycle, are infected by ingesting ova from soil or water contaminated by the feces of dogs .
Hydatid disease may develop in any organ of the body, most frequently in the liver and lung, but occasionally can affect other organs and regions [1–9]. The thyroid gland is very rarely affected by hydatid disease even in countries where the disease is endemic [2, 6]. Echinococcus granulosus can bypass the liver and lungs and settle in the thyroid gland via the systemic circulation, which enables it to reach the thyroid by way of first the carotids and then the thyroid arteries. A high circulatory flow rate in the thyroid gland may play an important role in the development of the thyroid hydatid cyst . The mechanism by which the relatively high thyroid blood flow relates to the disproportionately low incidence of thyroid cyst disease is unknown, but one theory implicates the relatively small caliber of the thyroid arteries together with their position at a right angle to the carotids, an anatomical arrangement that is thought to offer the thyroid gland some measure of protection against the invading parasite [2–4]. This report presents three original cases of thyroid hydatid cysts. One had disseminated hydatid disease and the thyroid was one of the disseminated organs. Another case was exciting because of an allergic reaction during surgical dissection. The last one had a combination of thyroid hydatid cyst and thyroid papillary carcinoma.
Hydatid disease is a parasitic infection with worldwide distribution, especially in sheep- and cattle-rearing regions of Australia, South America, the Middle East, South Africa, Eastern Europe, and the Mediterranean countries. The most frequent site of hydatid cystic disease is the liver because it is the first and largest filter of invading organisms migrating from the intestine via the portal stream. Parasite that manage to migrate through the hepatic filter can then enter the systemic circulation and settle in the lungs or, rarely, in other organs of the body including the spleen, brain, heart, bones, muscles, kidney, pancreas, retroperitoneum, breast, and thyroid gland [1, 5].
The thyroid gland is an extremely rare site of hydatid disease, even in countries with a high incidence of echinococcosis such as Turkey [3, 6, 7]. The incidence of thyroid gland involvement varies from 0 to 3.4 % in the literature [5, 9]. The parasitic embryo can enter the systemic circulation and lodge in the thyroid gland after either bypassing or passing through the hepatic microcirculation [2, 6–8]. Hydatid disease of the thyroid is divided into primary and secondary forms. The primary form refers to thyroid hydatid cysticosis diagnosed by clinical, radiologic and histopathological means, with no evidence of extrathyroidal hydatid disease. The secondary form is associated with additional hydatid disease of the liver, pulmonary system, or other organs. Hydatid cyst of the thyroid is generally the primary focus of the infestation; only a few patients are reported to have had secondary hydatid cysts in the liver, lung or other organ besides the thyroid [3, 6, 8]. Two of the cases reported in this study involved secondary hydatid disease, while one demonstrated primary hydatid disease.
Thyroid gland hydatid disease usually presents as a solitary cyst, and is normally a cold lesion according to radioactive iodine scanning of the thyroid. Hydatid cysts of the thyroid appear to be mostly asymptomatic until the size causes mechanical problems, leading to dyspnea, hoarseness of voice and dysphagia [4, 6–8]. These symptoms and signs stemming from an increase in the size of the cyst and impingement of the cyst on the surrounding tissues are likely to be frequently confused with those of thyroid cancers .
The complications associated with thyroid hydatid disease include anaphylaxis caused by a spontaneous or iatrogenic rupture, pyogenic abscess formation, secondary infections, impingement on surrounding structures, and spillage of the cystic content into the tracheal lumen secondary to a rupture of the cystic wall .
Goiter is the most common endocrine disorder requiring surgical management, particularly in areas where iodine deficiency is prevalent [6, 10]. Estimates show that approximately 30 % of people in Turkey suffer from goiter . Moreover, such disease as hydatid disease, which are among those severely affecting public health, remain endemic in the Eastern, Southern and Central Anatolia regions of Turkey. Therefore, hydatid disease should be included in the differential diagnoses of any patient evaluated for nodular goiter.
A medical publication review, performed by entering “thyroid”, “echinococcosis”, “hydatid cyst”, “hydatid disease” etc. into PubMed, Google Scholar and Medline databases, identified more than 60 published case reports of thyroid hydatid cysts. There was no published study reporting the concomitance of hydatid cyst and neoplasia either within one lobe or in contralateral lobes of the thyroid gland. So, the third case reported in this review is evidently the first known case of this phenomenon. However, the concomitance of a hydatid cyst and papillary carcinoma either within one lobe or in contralateral lobe of the thyroid was thought to be absolutely incidental. This concomitance indicates that more meticulous attention should be given to the differential diagnosis of the thyroid diseases characterized by calcification.
Diagnosis of hydatid disease is made primarily by patient history, physical examination, imaging modalities, serologic tests, and fine needle aspiration cytology (FNAC). Imaging modalities usually include ultrasonography, computed tomography (CT) and magnetic resonance imaging (MRI). Ultrasonography is highly efficient in detecting germinal vesicles in cystic lesions, which is important for a preoperative diagnosis of hydatidosis; CT-scan and MRI are often complementary diagnostic tools [2, 9]. Serological tests for hydatidosis at a clinician’s disposal include indirect hemagglutination (IHA), latex agglutination(LAT), Enzyme-linked immunosorbent assay (ELISA), and immune electrophoresis, but these have drawbacks of low diagnostic sensitivity and specificity so, therefore, have only limited use [6, 9]. Fine needle aspiration cytology (FNAC) is universally accepted as part of the clinical workup in cases of a single thyroid nodule. Although there is only one report in the literature mentioning allergic reaction after FNAC , it is not recommended, due to the risk of spreading cyst fluid or causing an anaphylactic reaction. Therefore, FNAC should be avoided when hydatid cyst of the thyroid is included in the differential diagnoses .
The treatment of choice for hydatid disease of the thyroid is surgical excision, as is the case elsewhere in the body, and radical cystic excision should be the goal of the procedure whenever possible [7, 8]. However, the authors also recommend subtotal thyroidectomy, especially when the cyst is small and confined to the thyroid lobe. Special care should be taken not to rupture the cyst during surgery because of the risk of disseminating the infestation or causing anaphylaxis. The antiparasitic agents, mebendazole, albendazole and praziquantel, can be used as the sole treatment for hydatid disease, or they can be used in conjunction with surgery to kill the live parasites pre-operatively and prevent any possible contamination caused by the spillage of cyst contents during the operation. In addition, antiparasitic agents are also necessary to avoid recurrence.
In conclusion, despite the rarity of hydatid disease in the thyroid gland, this diagnosis should not be overlooked, especially if the patient has hydatid cysts elsewhere in the body and/or has visited an endemic area.
Authors would like to thank the Editor of Journal of Inonu University Medical Faculty for allowing the use of first three figures.
Conflict of interest
The authors declare that there is no conflict of interest.