|Year : 2015 | Volume
| Issue : 1 | Page : 151-153
Diagnosis of primary hydatid cyst of thigh by fine needle aspiration cytology
KA Bothale, H Kolhe, SD Mahore, AR Wilkinson
Department of Pathology, NKP Salve Institute of Medical Sciences and Research Centre, Nagpur, Maharashtra, India
|Date of Submission||20-Mar-2014|
|Date of Acceptance||25-Jul-2014|
|Date of Web Publication||5-Jan-2015|
K A Bothale
Department of Pathology, NKP Salve Institute of Medical Sciences and Research Centre, Nagpur, Maharashtra
Source of Support: None, Conflict of Interest: None
Hydatidosis is a parasitic infestation caused by larval form of the tapeworm, Echinococcus granulosus. Primary hydatid cyst in the skeletal muscles and subcutaneous tissue of thigh without involving thoracic and abdominal organs is an exceptional entity, even in countries where the Echinococcus infestation is endemic. We report an unusual case of primary hydatid cyst of thigh in proximity to skeletal muscles. This case illustrates that echinococcal disease should be considered in the differential diagnosis of every subcutaneous cystic mass. This case is presented here for its rarity.
Keywords: Echinococcosis, hydatid disease, hydatidosis
|How to cite this article:|
Bothale K A, Kolhe H, Mahore S D, Wilkinson A R. Diagnosis of primary hydatid cyst of thigh by fine needle aspiration cytology. Indian J Med Microbiol 2015;33:151-3
|How to cite this URL:|
Bothale K A, Kolhe H, Mahore S D, Wilkinson A R. Diagnosis of primary hydatid cyst of thigh by fine needle aspiration cytology. Indian J Med Microbiol [serial online] 2015 [cited 2019 Jul 19];33:151-3. Available from: http://www.ijmm.org/text.asp?2015/33/1/151/148426
| ~ Introduction|| |
Hydatidosis is one of the most serious helminthic diseases of human being with worldwide distribution, caused by larval form of the cestode worm of Echinococcus. It may develop in any part of the body.  The liver is the most frequently involved organ (75%), followed by the lungs (15%). , According to various authors, primary subcutaneous and musculoskeletal echinococcosis is extremely rare.
| ~ Case Report|| |
A 70-year-old female presented with the complaint of a very slowly growing mass in the posterior aspect of left thigh for the past 2 years. Clinical diagnosis of soft tissue tumour was suggested. The patient was referred to Department of Pathology for Fine Needle Aspiration Cytology (FNAC) and routine investigations. Routine haematological and biochemical investigations were within normal limits. Local examination revealed large firm mass in the subcutaneous plane on posterior aspect of left thigh [Figure 1]. FNAC was performed using a 21-gauge needle. A turbid creamy fluid was aspirated. The post FNAC period was uneventful. There were no post-procedure complications like urticaria or anaphylactic reaction. The FNAC smears were stained with haematoxylin and eosin (H and E) and Papanicolaou stain. The smears showed many hooklets, scolices [Figure 2], calcified spherules [Figure 3] and fragment of laminated membranes [Figure 4]. The diagnosis of hydatid cyst was given. Subsequently, ultrasonography (USG) of the thigh was done. USG revealed multi-loculated cystic lesion with calcification in the posterior aspect of left thigh in the muscular and subcutaneous plane. Chest radiograph and USG of the thorax and abdomen were performed to rule out the lungs, kidney, or other common sites of involvement.
|Figure 1: Clinical photograph showing cystic lesion on posterior aspect of left thigh|
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|Figure 2: Photomicrograph of fine needle aspiration (FNA) smear showing hooklets and scolices (Papanicolaou stain, PAP stain; ×1000)|
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|Figure 3: Photomicrograph of FNA smear showing calcified corpuscles and hooklets (PAP stain, ×400)|
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|Figure 4: Photomicrograph of smear showing laminated membrane (Haematoxylin and eosin, H and E; ×400)|
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There was no history of trauma or fever. On examination, a non-tender cystic swelling was noted in the subcutaneous area of left thigh. The swelling was firm in consistency and free from the underlying structures. No obvious cystic lesion was detected at any other site. FNAC diagnosis of primary hydatid cyst of thigh was prescribed. Surgical excision of the hydatid cysts was performed.
Two intact multi-nodular cystic masses were received in the Department of Pathology. The larger mass measured 10 × 4.5 × 4 and the smaller mass measured 4.5 × 2.5 × 2 cm. The external surfaces of both the lesions were pale brown in colour. Cut surface showed thick-walled ectocysts with inner surface showing classical variable sized, milky-white thin-walled endocysts [Figure 5]. Histopathology revealed that the outer cyst wall consisted of fibrous tissue; skeletal muscle fibres and adipose tissue were adherent on the outer aspect. The inner cyst wall revealed laminated membrane and germinal layer. Therefore, on histopathology, cytological diagnosis of hydatid cyst in thigh was confirmed.
|Figure 5: Photomicrograph of gross appearance of cystic lesion showing ectocysts and endocysts|
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| ~ Discussion|| |
Incidence of musculoskeletal echinococcosis including involvement of subcutaneous tissue is 1-5.4% among all cases of hydatidosis. Soft tissue hydatid cysts occur in 2.3% of cases reported from endemic areas. They are usually associated with involvement of other solid organs. 
The mechanism of the primary subcutaneous localization is unclear. The ingested ova of parasite penetrate the intestinal wall, join the portal system and reach the liver, where most of them are caught in the hepatic sinusoids. A few ova pass through the liver and reach the lungs and systemic circulation, causing hydatidosis in other organs. A possible dissemination through lymphatic channels has also been reported. 
The majority of the hydatid cysts occur in the liver, the lungs, or both, but muscular and subcutaneous area is supposed to be an unfavourable site for infestation because of its high lactic acid concentration. The primary soft tissue involvement is very rare, causing a diagnostic challenge. 
Hydatidosis can be diagnosed preoperatively by FNAC with the direct demonstration of parasitic elements such as laminated membrane, hooklets, scolices with rostellum and calcified spherules in the stained smears of aspirate. In patients coming with a soft tissue cystic lesion, possibility of hydatidosis should be kept in mind as a differential diagnosis. As the post-procedure period was uneventful in the literature reviewed, FNAC can be considered as a safe and effective modality for the diagnosis of hydatid cyst. Minimal complications can be managed by anti-anaphylactics. ,
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]