Echinococcosis is a public health problem of global concern and is currently considered one of the “neglected tropical diseases” [20]. Hydatid cyst in the axilla can be considered to be primary only when no other cysts are present in any other part of the body [16]. Primary axillary hydatid cyst occurs as a result of dissemination of embryos of E. granulosus through hepatic and pulmonary filters, to eventually occupy atypical locations [7]. First reported in 1899, primary axillary hydatid cyst without involvement of any other organs is extremely rare, and only a handful of cases have been reported in published English literature since then. Table 1 summarizes the clinical presentations, investigations, and management of these cases [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18]. Our case also showed primary involvement of axilla without evidence of any other visceral involvement.
Clinical features depend on cyst site, size, pressure effects, and complications including rupture, infection, and immunologic reactions. Patients with axillary hydatid cyst usually present in the age between 25 and 45 years, with a female preponderance. The most common symptom is a gradually increasing mass with pain and discomfort. Our patient was a 32-year-old male and presented with a painless palpable mass in the left axilla, which is the common clinical feature. The differential diagnosis of a cystic axillary lesion can be:
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(i)
Non-parasitic cysts (ganglionic or inclusion cysts and cystic hygroma).
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(ii)
Parasitic cysts (coenurosis, toxoplasmosis, filariasis, and echinococcosis) [16].
Diagnosis is mainly based on radiological investigations and may be aided by serology. Ultrasonography, CECT, and MRI help to visualize the cyst’s relation to surrounding tissues, the wall of the cyst, and intraluminal daughter cysts. Imaging helps not only in diagnosis but also in cyst staging and follow-up after treatment [21]. However, when a cyst has atypical features, it is difficult to distinguish it from simple subcutaneous cyst, necrotic tumor, hematoma, or lymph node. In our patient, imaging confirmed the diagnosis and also helped in surgical planning. Serological tests can confirm diagnosis and are also useful for follow-up, but have a false positivity rate up to 33% [22]. Diagnostic aspiration cytology carries the risk of anaphylaxis, infection, and dissemination. In the cases reported so far in literature, some were diagnosed by radiological investigations [7, 8, 10, 11] and some by FNAC [1, 12] while most were diagnosed and confirmed only by intraoperative findings along with postoperative histopathological examination [2,3,4,5,6, 9, 13,14,15,16,17,18]. The indirect echinococcal hemagglutination test was positive in few cases [9, 12, 15, 17].
A preoperative diagnosis is important to avoid rupture and spillage of contents in systemic circulation during excision, which may lead to dissemination to distant organs to form additional cysts, local recurrence, and anaphylaxis.
Surgery remains the most effective treatment for soft-tissue hydatid disease. Total cystectomy with fibrous adventitia is the curative treatment [8]. The main principle of surgical treatment is to prevent complications such as compression of adjacent structures, infection, and cyst rupture.
Medical therapy is indicated for preoperative preparation, prophylaxis against postoperative recurrences, disseminated disease, pluri-visceral hydatid disease, and patients with contraindications for surgery or who cannot undergo radical surgery. Preoperative treatment with benzimidazole carbamate group of antibiotics has been reported to soften the cysts and to reduce intracystic pressure, enabling the surgical excision [23]. The most commonly used parasiticidal drugs from the above group are mebendazole (50 mg/kg/day) and albendazole (10 mg/kg/day in two divided doses), with the latter having better absorptive properties. It is recommended for a minimum period of 4 weeks preoperatively. Better results have been seen when three 28-day courses of 10 mg/kg/day in divided doses is given, separated by 2-week intervals. The drug acts by blocking glucose uptake in the parasite and depleting its glycogen store. However, experience with anti-helminthic agents in the treatment of soft-tissue hydatid disease is limited [7].
Our patient received albendazole 400 mg twice daily for three 28-day cycles separated by 2-week intervals. Following total cyst excision without rupture, he received postoperative albendazole 400 mg twice daily for another 4 weeks. No complications or recurrences were observed to date on follow-up.
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