.ABSTRACT
Background and Objectives: Cysticercosis is a common tropical disease. Human cysticercosis is caused by the dissemination of the embryo of Taenia soliumin the intestine via the hepatoportal system to the tissues and organs of the body. The organs most commonly affected are the subcutaneous tissues, skeletal muscles, lungs, brain, eyes, liver, and occasionally the heart, thyroid, and pancreas. Fine needle aspiration cytology (FNAC) plays an important role in prompt recognition of this disease.
Aims:To study the role of FNAC in the diagnosis of cysticercosis.
Methods: Fifteen patients with subcutaneous and intramuscular nodules, who were clinically diagnosed as lipoma, neurofibroma, lymphadenitis, cold abscess, epidermal inclusion cyst, sebaceous cyst,fibroadenoma and cysticercosis were included in the present study.
Results: In 4 (26.6%) cases, a definitive diagnosis of cysticercosis was obtained in the form of fragments of parasite bladder wall and, biopsy confirmed the diagnosis. In the rest 11 (73.3%) cases, larval fragments could not be identified on the aspirates and the diagnosis of parasitic inflammation was suggested on the basis of other cytomorphological findings. Follow-up biopsy confirmed the diagnosis of cysticercosis.
Conclusions: Cysticercosis is continuing to be a major health problem in developing countries. Fine needle aspiration cytology (FNAC) is cost effective and simple procedure. The cytological diagnosis is quite straightforward in cases where the actual parasite structure is identified in the smears. However, in other cases, presence of eosinophils, histiocytes, a typical granular dirty background, etc., are the features which should always alert the pathologist to this possibility.
Key words: Cysticercosis; Taenia Solium; Fine needle aspiration cytology.
Introduction
Cysticercosis is an infection with the larval (cysticercus) stage of Taenia solium[1-4].T. solium is a zoonotic cestode which has a complex two host life cycle [5].It is seen as cysts more commonly in the brain, muscle, heart and the orbit[1,6-8]. Humans are the only definitive hosts, harbouring the adult tapeworm in the gut without having significant symptoms [9]. Adult tapeworms have a life span of some years during which they produce millions of eggs which are intermittently released in the environment with the faeces [10]–[12].
Humans and pigs acquire cysticercosis by ingesting T. solium eggs by the faeco-oral route [5]. After the ingestion, embryos contained in the eggs are released, cross the intestinal mucosa and are then transported by the circulatory system and dispersed throughout the body producing cysts mainly in the central nervous system (CNS) and in striated muscles [5].
Humans can acquire cysticercosis ingesting T. solium eggs released by themselves (auto infestation) or by another tapeworm carrier living with them or involved in the preparation of food [13], [14]. In humans, the CNS is the most frequent localization of cysts which cause neurocysticercosis (NCC) [5].
It is endemic in America, Africa and Asia and linked to poverty, ignorance, lack of suitable diagnostic and management capacity and appropriate prevention and control strategies [15]. In India, it is more common in northern parts.
The preoperative diagnosis of cysticercosis can be made by radio imaging [Computed Tomography (CT) Scan and Magnetic Resonance Imaging (MRI)] and serological tests like Complement Fixation test, Hemagglutination, Radioimmunoassay and ELISA. CT scan and MRI, though sensitive in diagnosing cysticercosis; especially when the parasite involves the CNS, are very expensive. Moreover they provide only supportive diagnosis. Serological tests are useful if positive but cannot rule out the disease with negative results. False positivity is expected with the past parasitic infection or cross reactivity with other helminths.
Fine needle aspiration cytology (FNAC) is now available as a preoperative tool for the diagnosis of subcutaneous cysticercosis. The diagnosis is confirmed by the histopathological examination of the excised specimen.
The present study was done to analyse the cytomorphology of actual parasite and to study the cytological features suggestive of cysticercosis in those cases where the actual parasite could not be demonstrated.
MATERIALS AND METHODS
This is a hospital based study of 15 cases conducted at Department of Pathology, in a tertiary care hospital over a period of 24 months from June 2013 to June 2015.FNAC is an outpatient procedure in our hospital. 15 patients, who had superficial palpable subcutaneous andintramuscular lump, underwent FNAC during this period. FNAC was performed with 22-gauge needle. Aspirated material was smeared on the glass slides.In cases of fluid aspirate from cystic lesion, smears were prepared from cystic fluid after cytocentrifugation and stained with Papanicolaou stain after fixation in 95% alcohol. Subsequent excision biopsy was also evaluated. The sections were reviewed and findings were correlated with the cytological findings.
RESULTS
The study included 15 patients in the age group 8–65 years. Among 15 patients, 6 (40%) were females and 9 (60%) were males. All except two patients, presented with single, painless, superficial, slow-growing nodule of variable sizes while 2 patients presented with multiple nodules. 4(26.6%) cases presented with neck swelling, 5 (33.3%) with arm swelling,and 3(20%) with abdominal wall swelling, 1(6.6%) with swelling axilla, 1 (6.6%) with swelling cheek and 1 (6.6%) with swelling breast(Table 1). On local examination, all the swellings were soft to firm, nontender, and nodular. Provisional clinical diagnosis of Cysticercosis was made in only 2 cases, while the majority were clinically misdiagnosed as lipoma, neurofibroma, reactive lymphadenitis, tuberculous lymphadenitis,sebaceous cyst, fibroadenoma and benign tumour (Table 1). The aspirated material consisted of few drops to 4 mL fluid of variable consistency including clear fluid with or without granular deposit in 8 (53.3%)cases, purulent fluid in 5 (33.3%) cases, and blood-mixed fluid in 2 (13.3%) cases. No allergic reaction or any other complication was observed after the procedure.
In 4(26.6%) cases, a definite evidence of cysticercosis was observed in form of fragments of cysticercus bladder wall on cytology although the cytomorphologywas not exactly the same in all cases (Figure 1-A). None of them showed hooklets or scolex. Follow-up biopsy confirmed the diagnosis (Figure 2). All these cases showed varying proportion of inflammatory response with or without giant cells and granuloma.
In the rest 11(73.3%) cases, the cytological findings were very much suggestive of a parasitic cyst; however, no parasite could be seen. None of these cases showed hooklets or scolex on cytology. The cytology of these cases showed mild to moderate mixed inflammatory infiltrate, histiocytes, multinucleated giant cells, and epithelioid noncaseous granuloma in a dirty granular background (Figure 1-B). A cytological diagnosis of parasitic cyst was suggested and excision was advised. Follow-up biopsy confirmed the diagnosis of cysticercosis.
In this study, all cases of parasitic lesions or suspicious of parasitic lesion were associated with varying degree of mixed inflammatory response ranging from few histiocytes to marked mixed inflammatory cell infiltrate. Eosinophil was seen in only 7(46.6%) out of the 15 cases while lymphocytes, histiocytes including palisading histiocytes, neutrophil, foreign body giant cells, and epithelioid granuloma were seen in 3 (20%), 6 (40%), 3 (20%), 2 (13.3%), and 1 (6.6%) cases, respectively. Dirty granular background was seen in 7 (46.6%) cases (Table 2).
Table 1: Clinical Diagnosis in 15 cases included in the present study.
S. No. Site Clinical Diagnosis
1. Right arm Lipoma
2. Right cheek Sebaceous cyst
3. Left neck Reactive Lymphadenitis
4. Right arm Neurofibroma
5. Abdominal wall Benign tumour
6. Left arm Benign tumour
7. Abdominal wall Cysticercosis
8. Right neck Tuberculous lymhadenitis
9. Left Breast Fibroadenoma
10. Left arm Neurofibroma
11. Abdominal wall Benign tumour
12. Right neck Reactive lymphadenitis
13. Left neck Lymphadenitis
14. Right axilla Lipoma
15. Right arm Cysticercosis
Table 2: Cytological features in 15 cases included in present study.
S.No. Cytological Findings No. of Cases
1. Fragments of bladder wall of Cysticercus 4
2. Eosinophils 7
3. Hooklets 0
4. Lymphocytes 3
5. Histiocytes 6
6. Neutrophils 3
7. Foreign body Giant cells 2
8. Epithelioid granuloma 1
9. Dirty granular background 7
Figure 1: (A) Cytological smear showing bladder wall fragment of cysticercus cellulosae surrounded with inflammatory cells. (B) Aspirate showing a cluster of epithelioid histiocytes. (Papanicolaou stain)
Figure 2: Photomicrograph of tissue sections showing cysticercus larva enclosed in a thin fibrous cyst wall (H and E)
DISCUSSION
Cysticercosis in humans is an ancient disease and has even been detected in Egyptian mummies by paleoparasitologists [16]. Cysticercosis is the larval stage infection of the cestode Taenia solium. Humans are the only definitive host and can also act as intermediate hosts by ingestion of raw or poorly cooked vegetables or water contaminated with eggs or pork infested with larvae [17]. Cysticercosis is also common in vegetarians due to lack of basic sanitation facilities in developing countries [18].
Fully developed cysticerci are opalescent, milky white cysts, elongated to oval and about 1 cm in diameter. The cyst contains fluid and a single invaginated scolex. The scolex has a rostellum, four suckers and 22–32 small hooklets. The cyst wall is multilayered, 100–200 μm thick and covered by microvilli.
Subcutaneous or intramuscular palpable parasitic nodules are most commonly due to cysticercosis [19]. Most of these cases are clinically misdiagnosed as benign or malignant soft-tissue tumor or lymphadenitis depending on the site [20]. The diagnostic role of FNAC in cysticercosis was first emphasized by Kung et al. in 1989 [21]. Since then FNAC has become a pivotal tool in evaluating subcutaneous and muscle nodules caused by parasites [20]. The cytomorphological identification of larvae in FNAC smears by different workers has widened the diagnostic utility of FNAC in skin nodules [22, 23 and 24].
Essential for the cytodiagnosis of cysticercosis is identification of the parasitic fragments including its bladder wall and hooklets. The cytomorphology of cysticercosis varies from viable cysts through necrotic and calcified lesions. The most common finding in viable cysts is delicate fragments of bladder wall with tiny, parasitic nuclei in a clear, acellularbackground. Aspirates of necrotic lesions may contain fragments of bladder wall, invaginated portions, including calcerous corpuscles and detached single hooklets.Parasitic fragments may comprise bluish, fibrillary structures, sometimes with honeycombing, calcospherules, tegument thrown into rounded wavy folds, scolex with hooklets, and hyaline membrane surrounding it [25–27].
The physical factors such as the firm nonexpansile nature of the host tissue may limit the growth of the parasite and initiate the host inflammatory response. The presence of eosinophils, neutrophils, palisading histiocytes, giant cells, and atypical granular dirty background in an aspirate from a subcutaneous nodule should alert the cytopathologist of a parasitic infestation. Nonetheless, still in some cases of cysticercosis, none of these features may be present, and the inflammatory infiltrate may also be variable [20].Viable cysticerci may not cause any inflammatory response. However, when they degenerate, there is an infiltration of inflammatory cells, associated with the development of foreign bodygranulomas. The viable cyst and the necrotic and calcified lesions all have distinctive cytomorphological patterns. The viable cyst yields clear fluid and shows fragments of bladder wall in a clear acellular background. Finding an entire scolex in FNA is a rare event [28]. None of our cases showed hooklets or scolex on cytology.
Subcutaneous or intramuscular palpable parasitic nodule is most commonly due to cysticerci. Other parasites producing similar clinical presentation include Coenuri, the larval form of tapeworm and Multiceps and Spargana, larva of Spirometra Mansonoides [29]. Hydatid cyst caused by the larva of Echinococcus Granulosus can also occur in the subcutaneous tissue as an unusual presentation [30]. Cytomorphological details of the aspirate help to differentiate each other. Cysticerci and coenuri have suckers and hooklets where as spargna do not. The Coenures hasmultiple protoscolices distinguishing from cysticerci which has a single scolex, which is difficult to see in cytological smears [29]. Bladder wall is thin and membranous in cysticerci whereas it is thicker and lamellated in a hydatid cyst. Multiple small scolices in the aspirate obtained from the hydatid cyst are in contrast to the single scolex of cysticerci [29].
Conclusion
FNAC has emerged as an easy, quick, reliable, and sensitive diagnostic tool in identifying parasitic cyst. In FNAC smears if we are able to demonstrate parasitic bladder wall, tegument fragments, hooklets andcalcareous corpuscles, it helps to give definitive diagnosis and avoid open excision biopsy in many cases.
CONFLICTS OF INTEREST
The authors declare that there is no conflict of interests regarding the publication of this paper.
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