Echinococcosis multilocularis is a rare but dangerous zoonosis for which rodents are usually intermediate hosts and foxes are definitive hosts.1 Echinococcosis is regarded as a parasitic disease of an endemic nature. In Poland, the highest number of cases have been recorded in the Subcarpatia, Warmia-Masuria, and Lesser Poland regions.2 Due to an infiltrative growth of echinococcal cysts, the clinical picture most often resembles a slowly developing or indolent liver neoplasm.3

We present a case of a 70-year-old woman, a long-time resident of a rural area in the Subcarpathia region, with a history of complicated nephrolithiasis, ultimately leading to left sided nephrectomy, and subsequent end-stage renal disease. Renal replacement therapy was initiated as hemodialysis, until kidney transplantation (KTx) after 2 years. Following KTx, the patient was treated with a standard immunosuppressive regimen including glucocorticosteroids, tacrolimus, and mycophenolate mofetil, achieving maintenance of satisfactory graft function.

As part of transplant care, periodic imaging of the chest and abdomen was performed. In 2018, abdominal ultrasonography first revealed a 36 mm × 43 mm hyperechoic lesion in the liver. Further diagnostic workup included a contrast-enhanced abdominal and pelvic computed tomography (CT) scan, which showed normal parenchymal shading and smooth contours of the liver with a visible hypodense lesion in the 6th segment. It was described as a slightly polycystic mass in all phases of examination, interspaced with small septa and only partially aligned with the remaining liver parenchyma in later phases of examination (Figure 1A and 1B). The CT image was equivocal, and differential diagnosis included atypical hemangioma, abscess, focal nodular hyperplasia with a high degree of dysplasia, and cystadenoma from the biliary tract. Over the next 2 years of follow-up imaging, the lesion remained stable in size until 2020, when significant progression of its dimensions was witnessed (Figure 1C). Further magnetic resonance imaging of the liver, pancreas, biliary tract, epigastrium (with and without contrast), revealed a nonenlarged liver, with a lesion sized 59 mm × 60 mm × 68 mm within the 6th and 7th segment, described as having a polycyclic outline and multicystic structure. The central region was more solid in nature, while numerous peripheral cysts contained fluid, and were separated by thin walls (Figure 1D–1F). The patient was qualified for right-sided hemihepatectomy with adjacent lymph node excision; the lesion was successfully removed with a preserved margin. Histopathologic examination further revealed a multicellular tapeworm cyst surrounded by a band of granulation tissue visible within the liver parenchyma and in the dilated bile ducts (Figure 1G and 1H). The patient was consulted by an infectious disease specialist, serology confirmation was obtained (anti-Echinococcus spp. immunoglobulin G antibodies were positive), and albendazole treatment was implemented for a period of 2 years. The patient has completed treatment and remains without any symptoms, with stable graft function.

Figure 1. A, B – contrast-enhanced computed tomography showing a hypodense focal lesion with irregular polycyclic contours and density of about 35 Hounsfield units in the 6th segment of the liver, with no enhancement after contrast agent administration (arrows) in the coronal (A) and axial (B) view; C – abdominal ultrasound showing a heterogeneous hyperechoic lesion measuring 59 mm × 46 mm located in the 6th and 7th segment of the liver (arrow); D–F – magnetic resonance imaging (MRI) showing the 6th and 7th segment of the liver with the lesion measuring 59 mm × 60 mm × 68 mm, with polycyclic contours, multicystic structure, more solid in the central part, with features of postcontrast enhancement and poorly marked diffusion restriction within the solid elements, and septa mainly in the peripheral parts of the lesion (arrows): coronal T2-weighted MRI (D), axial T1-weighted contrast-enhanced MRI (E), diffusion-weighted imaging (F); G – cystic spaces lined with fibrous tissue (arrows) and inflamed liver tissue in the lower part of the panel (hematoxylin and eosin [HE] staining, magnification × 100); H – fibrous wall of the cystic space containing a part of the worm body (arrow) and inflamed liver tissue in the upper part of the panel (HE staining, magnification × 200)

The mortality rate estimate of untreated echinococcosis usually reaches 90% within 10 years of diagnosis, while surgical treatment and chemotherapy reduces it to approximately 10%–14%.4 As multicellular echinococcosis is increasingly recognized in immunocompromised patients, the benefits of serologic screening (enzyme-linked immunosorbent assay) prior to initiation of long-term immunosuppressive therapy require appraisal, especially in patients from endemic areas.5