The Great Masquerader: A Rare Case of Hydatid Cyst in the Neck

By Muhammad Aliyan Ahmed¹, Ali Aamir¹, Uzair Yaqoob¹, Muhammad Adil Khatri²

Affiliations

1. Department of Neurosurgery, Shaheed Mohtarma Benazir Bhutto Institute of Trauma, Civil Hospital, Karachi, Pakistan
2. Department of Neurosurgery, Jinnah Sindh Medical University, Karachi, Pakistan

ABSTRACT
Hydatid disease, caused by the larval stage of Echinococcus granulosus, usually affects the liver and lungs. Primary neck involvement is rare (<2%) and often mimics other cystic neck lesions, causing diagnostic delays. The authors report a case of a 30-year woman from a rural area with a gradually enlarging, painless right neck swelling for one year. Ultrasonography suggested a cold abscess, however, MRI showed a cystic lesion with an internal floating membrane, and serology was positive for Echinococcus antibodies. Despite albendazole therapy, the swelling persisted, leading to surgical excision. Intraoperatively, the cyst ruptured but was managed with irrigation using scolicidal agents. Histopathology confirmed a hydatid cyst. The patient completed postoperative albendazole and remained recurrence-free for six months. Hydatid cysts should be considered in the differential diagnosis of neck swellings in endemic areas. Early imaging, serology, and combined surgical-medical therapy are essential for successful management.

Key Words: Hydatid cyst, Echinococcus, Neck swelling, Tapeworm.

INTRODUCTION

Hydatid disease is a parasitic infection caused by the larval stage of Echinococcus tapeworms, characterised by cyst formation, most commonly in the liver and lungs. Head and neck involvement is exceedingly rare (<2%) and poses diagnostic challenges due to its atypical location and resemblance to other neck lesions.¹ Diagnosis may be aided by ultrasonography, computed tomography (CT), and occasionally fine-needle aspiration cytology (FNAC).^1-3

Although hydatid cysts occur in the brain, spine, and other unusual sites, primary neck involvement is seldom seen in neurosurgical practice. This rarity highlights the significance of the present case, detailing diagnosis, surgical management, and postoperative outcome in a young woman.

CASE  REPORT

A 30-year female with no known comorbidities, presented to the outpatient department with a swelling on the right side of the neck, present for 12 months. The swelling had a gradual onset, progressive enlargement, and was intermittently painful, with relief on over-the-counter analgesics.

There was no history of discharge, ulceration, fever, weight loss, prior surgery, addictions, or contact with tuberculosis.

On examination, there was a single, globular swelling in the posterior triangle of the neck, measuring approximately 5 × 5 cm, extending from the occiput to the nape. The swelling was soft to cystic in consistency, non-mobile, and non-tender. It was not adherent to the overlying skin but was fixed to the underlying musculature. No punctum or sinus was present. There was no bruit on auscultation, and regional lymph nodes were not enlarged. Ultrasonography revealed a well-defined hypoechoic cystic lesion measuring 5.3 × 4.6 × 6.4 cm on the right lateral aspect of the neck, initially suggestive of a cold abscess. FNAC demonstrated scattered keratin flakes and mildly acellular keratinous material. Complete blood count (CBC) was within normal limits, whereas liver enzymes were mildly elevated. There was no laboratory evidence of systemic infection. CT of the neck demonstrated a hypodense lesion in the right neck region measuring approximately 5.7 × 6.0 cm, with peripheral post-contrast enhancement. Within the lesion, a second similar-density structure representing floating membranes was noted, measuring 7 cm craniocaudally. The mass caused focal skin bulging to the midline and displaced the adjacent erector spinae and paravertebral muscles medially (Figure 1).

Magnetic resonance imaging (MRI) of the neck revealed a well-defined, round-to-oval cystic lesion with abnormal signal intensity, and an internal detached floating membrane within the soft tissues of the right neck region. The lesion extended into the right paraspinal area from the C1 to C4 vertebral levels. It demons- trated iso-intense signal on T1-weighted imaging (T1WI) and hyperintense signal on T2-weighted imaging (T2WI), with patchy areas of restricted diffusion on diffusion-weighted imaging (DWI) and corresponding low signal intensity on apparent diffusion coefficient (ADC) mapping. Post-contrast sequences showed peripheral enhancements without surrounding oedema. The lesion measured approximately 4.4 × 7.2 cm (anteroposterior × transverse) on axial T2WI and 6.9 cm craniocaudally on coronal T2WI. Posterolaterally, it displaced the splenius capitis, semispinalis capitis, longissimus capitis, and trapezius muscles on the right side; anteromedially, it compressed and displaced the right oblique capitis inferiorly; and medially, it displaced the ligamentum nuchae towards the left (Figure 2 and 3). The diagnosis was confirmed by  a  positive  Echinococcus  antibody  titre.

Figure 1: Coronal (A) and axial (B) contrast-enhanced CT scans of the neck demonstrating a hypodense lesion in the right paravertebral region with peripheral post-contrast enhancement. An internal similar-density component, consistent with floating membranes, is seen measuring approximately 7 cm craniocaudally, producing focal skin bulging toward the midline and displacing the adjacent erector spinae and paravertebral muscles medially.

Figure 2: T2-weighted sagittal (A, B) and axial (C, D) MRI images of the neck demonstrating a well-defined, hyperintense, round-to-oval cystic lesion with an internal detached floating membrane within the soft tissues of the right side of the neck.

Abdominal ultrasonography and transthoracic echocardio- graphy were performed to exclude cystic lesions in the abdomen and heart, with both examinations yielding unremarkable findings. The patient was commenced on albendazole 400 mg twice daily. However, as the swelling remained symptomatic and showed no improvement after 10 days of medical therapy,  surgical  excision  was  planned.

Figure 3: Post-contrast T1-weighted sagittal (A, B) and coronal (C, D) MRI images of the neck showing a well-defined, round-to-oval cystic lesion with an internal detached floating membrane within the soft tissues of the right neck, demonstrating peripheral contrast enhancement.

Figure  4:  Perioperative  pictures  of  the  excised  hydatid  cyst.

Under general anaesthesia, an elliptical incision was made over the swelling, and a subcutaneous plane was dissected through the musculature until the cyst capsule was reached. The lesion was carefully mobilised from the surrounding tissues; however, intraoperative rupture of the capsule occurred, releasing purulent yellowish fluid. The cyst was completely excised, haemostasis was achieved, and the surgical cavity was irrigated sequentially with hydrogen peroxide, normal saline, and hypertonic saline (Figure 4). The excised tissue was sent for histopathological examination, which confirmed the diagnosis of a hydatid cyst. Postoperatively, the patient remained haemodynamically stable and was discharged on the second postoperative day with a prescription for albendazole 400 mg twice daily and analgesics. At the six-month follow-up, the patient was asymptomatic, with no evidence of recurrent swelling. The surgical wound had healed well, and the patient remained pain-free.

DISCUSSION

Hydatid disease is a zoonotic infection caused by the larval stage of Echinococcus granulosus.⁴ Humans become accidental intermediate hosts by ingesting food or water contaminated with Echinococcus eggs, or through direct contact with definitive hosts, typically domestic dogs. After hatching in the small intestine, oncospheres penetrate the mucosa and disseminate via the portal venous or lymphatic system, most commonly lodging in the hepatic sinusoids. A smaller proportion bypasses the liver to reach the lungs and systemic circulation, making these two organs the most frequent sites of involvement.^2,5 Primary hydatid disease of the head and neck region is rare, accounting for only 1–2% of cases.⁶

The present case adds to the limited literature on hydatid disease of the neck and illustrates the diagnostic and surgical challenges associated with this atypical location. The patient’s presentation, a slowly enlarging, painless neck swelling over one year with intermittent discomfort, reflects the hallmark growth pattern of hydatid cysts, which may remain asymptomatic until they compress adjacent structures.⁷ The rarity of neck involvement often leads to misdiagnosis or delayed diagnosis. Ultrasonographic features of hydatid cysts in the neck are generally similar to those in visceral sites.⁸ In this case, initial ultrasonography suggested a cold abscess, but MRI demonstrated a detached internal membrane, and a positive Echinococcus antibody titre confirmed the diagnosis. While FNAC is a common diagnostic tool for thyroid and other cystic lesions, its use in suspected hydatid disease is generally discouraged due to the risks of anaphylaxis and dissemination.⁹ Nevertheless, in some cases, including ours, hydatid cysts have been incidentally diagnosed histopathologically without procedural complications.¹⁰

Surgical excision remains the definitive treatment for hydatid disease regardless of location.^11,12 The primary surgical principle is complete removal of the cyst without spillage, thereby minimising recurrence and secondary infection. In this case, intraoperative rupture occurred despite meticulous dissection, releasing purulent yellowish fluid. Prompt and thorough irrigation with hydrogen peroxide, normal saline, and hypertonic saline, agents with established scolicidal activity, was performed to reduce the risk of dissemination and anaphylaxis. Postoperatively, albendazole 400 mg twice daily was continued to eradicate residual parasitic elements and prevent recurrence, consistent with current treatment guidelines.¹¹ The patient remained recurrence-free at six-month follow-up.

Hydatid cysts of the neck have been sporadically reported and are thought to occur via haematogenous dissemination or as secondary deposits from primary lesions that may have resolved or remained undetected. The absence of direct portal venous drainage to the neck likely accounts for their rarity. This case underscores the need for heightened clinical suspicion in endemic regions, particularly for atypical cystic lesions of the neck. Public health measures, including improved livestock management, canine deworming, and community education, remain essential in reducing disease incidence. Targeted screening of at-risk populations through imaging and serology may facilitate earlier diagnosis and prevent complications associated with delayed management.

To conclude, primary hydatid disease of the neck is an exceptionally rare presentation that can mimic other cystic lesions, often leading to diagnostic delays. This case highlights the importance of considering hydatid disease in the differential diagnosis of neck swellings in endemic areas and underscores the role of advanced imaging and serological testing in establishing the diagnosis. Complete surgical excision combined with perioperative antiparasitic therapy remains the corner- stone of management, even in anatomically challenging sites, to achieve optimal outcomes and prevent recurrence.

PATIENT’S  CONSENT: 
Informed consent was obtained from the patient to publish the data concerning this case.

COMPETING  INTEREST: 
The  authors  declared  no  conflict  of  interest.

AUTHORS’  CONTRIBUTION:
MAA, UY: Conception and design of the study, acquisition of the data, and drafting of the manuscript.
AA, MAK: Conception and design of the study, acquisition of the data, and critical revision of the manuscript critically for important intellectual content.
All authors approved the final version of the manuscript to be published.
 

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