Hydatid Cyst of Parotid Gland: An Unusual Case Diagnosed by Fine Needle Aspiration Biopsy
Tuba KARA1, Rabia BOZDOĞAN ARPACI1, Yusuf VAYISOĞLU2, Ebru SERİNSÖZ1, Didar GÜRSOY1, Anıl ÖZGÜR3, Demir APAYDIN3, Cengiz ÖZCAN2
1Departments of Pathology, Mersin University, Faculty of Medicine, MERSİN, TURKEY
2Departments of Otorhinolaryngology, Mersin University, Faculty of Medicine, MERSİN, TURKEY
3Departments of Radiology, Mersin University, Faculty of Medicine, MERSİN, TURKEY
Keywords: Diagnosis, Fine-needle biopsy, Echinococcosis, Parotid gland
Hydatid disease is a zoonotic disease caused by the parasite
Echinococcus granulosus. This infection frequently infects the
liver and the lung and even in endemic regions rarely occurs in the
head and neck region. This is also true for the parotid gland. The
diagnosis relies on imaging techniques and the medical history.
Another method that is helpful in the diagnosis is serological tests.
Fine-needle aspiration biopsy is usually not recommended due to the
potential risk of anaphylactic shock or spreading of daughter cysts.
The preferred treatment method of hydatid cysts in the salivary gland
is surgical excision. We introduce a rare case of hydatid cyst in the
parotid gland diagnosed preoperatively by fine-needle aspiration
biopsy and discuss the differential diagnosis.
Echinococcus granulosus (E. granulosus) causes hydatid
disease, which is a momentous infection and still common
in Mediterranean countries1
. The liver is the most
frequently (65%) involved organ, but the infection also
shows a multi-organ involvement, particularly in the lung,
spleen, kidneys, heart, bone, and central nervous system2
. In the life cycle of the parasite, dogs (and other canines)
are the definitive hosts and a variety of organisms such as
sheep, goats, horses, and humans are the intermediate hosts.
Intermediate hosts ingest eggs by the faecal-oral route and
the embryos are released in the small intestine and then
enter the portal circulation and travel to visceral capillary
beds, usually the liver or the lung, and develop into cystic
lesions. However, several eggs may pass through the liver
to the systemic circulation and heart and localize in many
organs and areas such as the orbit, heart, and bladder3,4
Salivary gland lesions have traditionally been investigated
by fine-needle aspiration biopsy (FNAB). This is a simple
technique that is well-tolerated by patients and hence can be
performed repeatedly if required5. However this method
has been used as a diagnostic procedure for hydatid cyst
based on a case series involving different organs and many
single case reports6.
The head and neck region and especially the parotid gland
is an infrequent localisation for hydatid cyst, even in
geographical areas where echinococcosis is endemic. Such
involvement was first reported in 1947 by Martini and there
have only been a few case reports in the English literature ever
since7-9. It is generally not considered in the differential
diagnosis of parotid lesions preoperatively as it is a rare
entity in this localisation. Herein, we present hydatid disease
localised in the parotid gland and discuss the preoperative
diagnosis with FNAB and the differential diagnosis.
A 54-year-old woman presented at the otorhinolaryngology
clinic with a complaint of rapidly growing mass in the left
parotid gland for the last month that was accompanied by
mild pain. There was no record of fever or weight loss within
this time and nothing else remarkable in the history. Physical
examination revealed a 3×2 cm irregular semimobile mass
in the left parotid gland. Ultrasonographic examination of
the neck region showed an unechoic well-defined, circular
mass with acoustic enhancement in the left parotid gland.
FNAB was performed under ultrasonographic control.
Serous fluid was aspirated from the mass, indicating that
the mass was cystic and most likely benign. The first FNAB
of the lesion yielded no definitive diagnosis. Psammomalike
bodies were seen in the cytology specimen and renewed aspiration was recommended for the final diagnosis (Figure
). The second aspiration showed scolices, hooklets,
inflammatory cells and histiocytes (Figure 2
), and was
reported as hydatid cyst. The re-examination of the first
aspiration revealed that the psammoma like bodies were
the protoscolex of the parasite.
Computed tomography (CT) scan of the thorax,
ultrasonography (USG) of the abdomen, and urologic
examination were performed to rule out the contingency of
dissemination into the viscera, and revealed no involvement
of extracervical sites. The clinician therefore decided to
remove the mass. During surgery, the cystic lesion has
replaced most of the inferior part of the left parotid gland,
and frozen-section studies confirmed the diagnosis of
hydatidosis (Figure 4). Superficial parotidectomy was therefore performed. Light microscopic examination with
clear evidence of hydatid scolices and laminated membrane
verified the preliminary diagnosis of hydatidosis (Figure 5).
Albendazole therapy was administered for 2 months after
the operation with liver enzyme and blood count followup.
The patient was asymptomatic with no recurrence of the
hydatid cyst at the 1-year follow-up.
Click Here to Zoom
|Figure 3: Hooklets between inflammatory cells and histiocytes
Click Here to Zoom
|Figure 4: Typical laminated membrane of the cyst replaced most
of the inferior part of the parotid gland.
Echinococcosis or hydatid disease is a parasitic infestation
caused by larvae of the tapeworm E. granulosus. Both
animals and humans are involved as an accidental host,
do not play a role in the biological cycle, and are usually
infected by handling an infected dog9
. Hydatid cysts
are common in the liver and lung, whereas head and neck
region involvement is a rare finding. There are only a small
number of case reports in the literatüre9-13
Although most hydatid cysts are slow-growing and
asymptomatic, the mass effect of the cyst on the infected
organ may lead to emergence of clinical symptoms.
Knowledge of the involved area in the patient may enable
the consideration of hydatid cyst in the differential
diagnosis but preoperative diagnosis may not be possible
unless radiological findings are present or suspicious for
hydatid cyst10. Hydatid disease should be considered in
the differential diagnosis of congenital and acquired cystic
lesions of the parotid gland in endemic areas. Dermoid and
epidermoid cysts may also be present in the parotid gland.
The first branchial cleft cysts and rarely cystic hygromas can
also be seen in these glands. Some benign and malignant
tumors of parotid gland may also present as cystic masses9. Imaging methods such as USG, CT, and magnetic
resonance imaging (MRI) have an important role in the
diagnosis of hydatid disease. USG is the preferred method
for the demonstration of pathognomonic criteria such as
the hydatid sands besides floating membranes, daughter
cysts, and also vesicles in completely cystic lesions14.
MRI is the most useful imaging technique for the diagnosis
of cases that do not have characteristic USG features of
Serological tests, such as agglutination methods, immunoelectrophoresis,
skin tests, as well as enzyme-linked
immunosorbent assay (ELISA) have low diagnostic
sensitivity and specificity but are the first line laboratory
tests used to confirm the diagnosis16. These tests are more
important during follow-up17. Imaging methods are
more sensitive than serology, and a USG or CT examination
showing the characteristic features of hydatid cyst would
suggest the diagnosis in case of negative serological results16. A through systemic examination must be done to rule
out the involvement of other organs, and especially the liver
and lungs, when hydatid disease is found2.
The use of FNAB in the diagnosis of hydatid disease is still
controversial. In general, it is not recommended due to the
potential risk of precipitating acute anaphylaxis or spreading
daughter cysts18. This risk seems to have attracted great
attention in the past but there are also a large number
of articles indicating that diagnosing hydatid disease
cytologically is a safe procedure without complications19.
Only one case of cervical hydatid cyst that developed an
anaphylactic reaction during the FNAB procedure has been
reported so far. Although there are so few reported cases of
allergy, adequate emergency precautions should always be
taken to overcome these situations20. Clinicians should
be aware of the possibility of the cervical localisation
of the hydatid cyst and should avoid biopsy procedures
before surgery due to the minimal but dangerous risks. No
anaphylactic reaction was observed in our case and this is
the first case of hydatid cyst located in the parotid gland
diagnosed by FNAB to the best of our knowledge.
Hydatid cyst uncommonly occurs in the head and neck
region but it should be considered in the differential
diagnosis of cervical masses, especially in endemic areas.
Imaging methods such as USG, CT, and MRI play an
important role in the diagnosis of hydatid disease. However,
the initial diagnosis was made by FNAB in our case.
Although the technique helps make the diagnosis before
surgery, the risk of causing an anaphylactic reaction should
always be kept in mind.
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