Discussion
Echinococcus is a genus of tapeworms that cause a parasitic disease in humans and animals known as echinococcosis. Cystic echinococcosis is the most common of the four main types of the disease, also known as HD. The larval stage of Echinococcus granulosus is responsible for causing HD (8). It is an endemic disease in a number of areas, including the Mediterranean, South America, North and East Africa, the Middle East, China, Australia and Russia (10). It is primarily observed in places where sheep and cattle are raised (11).
The Echinococcus life cycle requires a definitive host and an intermediate host. Humans can become intermediate hosts (8) when they become accidentally infected by ingesting the eggs of the parasite, which are shed in the feces of infected dogs (12). This can occur through close contact with infected dogs, particularly when handwashing is omitted following direct contact or when contaminated food or water is ingested. The ingested eggs travel to the human intestines, where they hatch and release oncospheres (1). These embryos then migrate through the bloodstream to different organs, most commonly the liver (in 75% of cases) and lungs (in 15% of cases), followed by other organs (in 10% of cases) (3,13). The embryos develop into HCs in these organs, which can grow slowly over the years. The most probable route for disseminating HD is the bowel lymphatics into the systemic bloodstream (14).
The lymphatic pathways between the liver and breast (Gerota's pathway) are a possible route for breast involvement by HD (14). Herein, following a literature review, it was found that the reported cases mostly occurred between the ages of 30 and 50 years, usually presenting with a history of a painless, slowly enlarging breast mass (3,12,13). A literature review was conducted to identify relevant reports on BHC, filtered by the well-known predatory lists (15). The process involved a Google Scholar search employing the ‘breast hydatid cyst’ as a key word. In total, 13 reports on BHCs were identified from 2021 to 2024, of which 11 reports were summarized in the present study (2,8,16-24). Among these, rural residency was reported in 3 cases, with an age range of 18 to 75 years and a mean age of 37.6 years. The majority of these cases (90.9%) presented with a breast lump (Table I). In their systematic review, Mutafchiyski et al (14) reported that in a total of 52 cases of BHC, the duration of the presentation ranged from 4 months to 19 years. The majority of cases involved a single cyst, with only 2 cases having multiple cysts (14). In a case series, Tavakoli et al (10) described 6 cases with symptom durations ranging from 8 months to 3 years, while Koc et al (13) reported a case with a longstanding history before presentation, a finding similar to the case presented herein. Among the reviewed cases that specified the duration of presentation, this ranged from 2 to 36 months, with a mean of 15.4 months. The left breast was the most frequently affected side (72.7%), and the upper quadrant was the most commonly involved region (54.5%). In the patient in the present case report, the lesion was located in the lateral central portion of the left breast.
BHC can mimic a simple cyst, fibroadenoma, phyllodes tumor, chronic abscess, or cancer (8,12). Fibroadenomas have an excellent prognosis with minimal malignant potential and may even regress spontaneously (25). BHC also exhibits a benign course following resection; however, follow-up is recommended to monitor for recurrence (26). By contrast, breast carcinoma has a stage-dependent prognosis, with the 5-year survival >99% in localized disease, yet decreasing to ~87% with regional spread and ~32% with metastasis (27).
Generally, HC is an essential consideration in the differential diagnosis of a palpable breast mass, particularly in individuals from regions where HD is endemic (2). Therefore, a triple assessment is valuable for excluding malignancy in any breast mass, including a comprehensive history and physical examination, radiological imaging and histopathological analysis (28). Clinically, HC appears as a firm, mobile, often painless lump of variable size with a regular border (1). Imaging may be helpful in the diagnosis of breast HD, although it is usually not conclusive (1,12). Breast U/S is the method of choice for evaluating this type of cystic lesion. It has a sensitivity of 88-98% and a specificity of 95-100% (8,10). Breast U/S can indicate a well-defined, sometimes lobulated mass with mixed internal echoes, potentially containing both cystic and solid areas. According to the classification presented in the study by Gharbi et al (29), five ultrasonographic features have been described: An uninoculated pure fluid collection (type I); a fluid collection with a split wall (type II); a multi-vesicular, multiseptated cyst with daughter cysts (type III); a mass with a heterogeneous echo pattern (type IV); and a mass with reflecting thick walls (type V). Types II and III HC have more specific diagnostic imaging features than the other types. MMG may illustrate a non-specific, well-circumscribed, round, or oval-shaped mass with internal ring-shaped structures (1). Calcifications within the cyst wall or daughter cysts may be visualized (20). Upon imaging, the case in the present study was found to have type IV features (a mass with a heterogeneous echo pattern) according to the classification presented in the study by Gharbi et al (29). However, fibroadenomas typically appear as well-circumscribed, oval, or lobulated masses with smooth, sharp margins on mammography and as uniformly hypoechoic, circumscribed lesions on ultrasound (25). By contrast, invasive breast carcinomas typically present as irregular or spiculated high-density masses (often accompanied by microcalcifications) on MMG and as angular, non-parallel hypoechoic lesions with posterior acoustic shadowing on ultrasound (30,31).
A breast MRI can be a helpful tool for the diagnosis of HC in the breast (13), as it can provide more detailed information about the size, location and characteristics of the cyst. A well-defined cystic lesion with a smooth wall, perilesional edema (fluid build-up around the cyst), daughter cysts (smaller cysts within the larger cyst), T1 hypo-intensity (dark signal on T1-weighted images), T2 hyperintensity (bright signal on T2-weighted images) and peripheral rim enhancement (increased uptake of contrast dye along the rim of the cyst) are the MRI findings that are suggestive of an HC (10,20). Notably, these findings are not specific to HCs and can also be observed in other breast lesions (13). The results of a breast MRI need to be interpreted in conjunction with other clinical information, such as the medical history of the patient and the results of the physical examination, in order to ensure an accurate diagnosis. In their systematic review, Mutafchiyski et al (14) reported that MRI was used as a diagnostic modality in only a few cases. Among the 11 reviewed cases in the present study, only 1 case had undergone a breast MRI (21).
Fine needle aspiration cytology was previously considered controversial in the pre-operative diagnosis of HC in the case that the U/S examination suggested the disease, as it may lead to spillage and anaphylactic reaction (10,24). Recent literature, however, has concluded that the procedure may be safe, fast and inexpensive (2,12,32). The microscopic identification of the scolices or hooklets in the fluid is required for the diagnosis (12,14). Serological tests can be used for diagnosis, screening and post-operative follow-up, including enzyme-linked immunosorbent assay (ELISA), hydatid immunoelectrophoresis, latex agglutination and an indirect hemagglutination test. The sensitivity of ELISA ranges from 80-100%, and its specificity ranges from 88-96% for hepatic cysts. The sensitivity of the test ranges from 50 to 56% for lung HD and from 25 to 65% for HD of other organs (4). Since serological tests demonstrate variable sensitivity in diagnosing HCs at different anatomical sites, the development of a rapid and reliable serological assay for extrapulmonary HC remains necessary (33). Therefore, U/S, MRI or MMG may help rule out the presence of HC in the breast (13,21), as in the case in the present study.
Surgical intervention, puncture aspiration injection and re-aspiration, a ‘watch and wait’ approach, and chemotherapy are the main treatment options for HC (4,8). However, complete surgical excision is the best diagnostic and therapeutic approach (14). By contrast, fibroadenomas are usually observed or removed by local excision if large or symptomatic, while invasive carcinomas require oncologic surgery, often with additional radiotherapy, chemotherapy, or hormonal therapy depending on stage and tumor biology (25,34).
A definitive diagnosis of HC is often achieved through a post-operative histopathological examination (8). HCs have a multilayered wall composed of a laminated membrane and a germinal layer that produces protoscoleces and daughter vesicles, typically accompanied by surrounding fibrosis and inflammation (26). However, fibroadenomas are benign, well-circumscribed tumors of stromal and ductal elements with intact myoepithelial lining and no atypia (25). Breast carcinomas exhibit malignant invasion beyond the basement membrane, characterized by nuclear pleomorphism, increased mitotic activity, and disorganized growth patterns (34). Preoperative chemotherapeutic agents, such as albendazole, can reduce the postoperative recurrence rate (2,3), which ranges from 2 to 25% (3). However, among the cases reviewed herein, only 3 cases used pre-operative albendazole (8,16,21). The mortality rate due to echinococcosis is very low, ranging between 0.29 to 0.6% (4). Complete surgical excision with intact borders followed by a course of albendazole was the favored treatment in many studies (1,2,8,25). Of the cases reviewed herein, 4 cases were administered post-operative albendazole (2,17-19). The current case underwent the complete surgical excision of the cyst without postoperative complications. Histopathological examination confirmed BHC. Following a 4-month follow-up, no recurrence was reported. Further studies with larger sample sizes and more robust designs are warranted to elucidate the mechanisms underlying BHC occurrence.
In conclusion, BHC can remain asymptomatic for a long period of time and may masquerade as a gradually enlarging, painless breast mass.