Hydatid cyst disease is a zoonotic infection caused by the genus Echinococcus. Hydatid cysts are usually located in the liver or lungs, whereas the brain is an unusual location.[1] This current article presents a patient with a cerebral alveolar echinococcosis misdiagnosed as a metastatic tumor.
A 45-year-old male patient was diagnosed with an intracranial mass suggesting a metastasis in the frontal region shown in the cranial computed tomography (CT) scan following a cranial trauma. The medical history of the patient informed that he had no complaints other than headaches. The contrast-enhanced cranial diffusion MR imaging revealed a subcortical mass surrounded with significant vasogenic edema with a diameter of approximately 2 cm in the left frontal lobe of the patient. The postcontrast imaging noted a heterogeneous contrast uptake more remarkable in the periphery. In addition, a nodular lesion of 6 mm diameter with a peripheral vasogenic edema was observed at the right superior frontal gyrus [Figure 1]. The mass was excised almost completely by means of bipolar cautery and aspirator. In the macroscopic examination, there were four yellow-beige tissues, the largest 0.6 × 0.4 × 0.3 cm and the smallest 0.4 × 0.3 × 0.2 cm.
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Figure 1: T1 (a) isointense in the left frontal lobe, T2 (b) and FLAIR (c) hypointense, lesion in the postcontrast series (d) with circumferentially intense heterogeneous contrast and peripheral intense vasogenic edema the enlarged space-occupying lesion
The histopathological examination suggested cuticles, demonstrating acellular structures with laminated walls in widespread necrotic tissue. There was a diffuse histiocytic and lymphoplasmacytic cellular inflammatory infiltrate in the white matter [Figure 2]. The histochemical staining of the eosinophilic cuticular membrane with PAS and Grocott was positive [Figure 3]. These findings were interpreted in favor of the diagnosis of a hydatid cyst of Echinococcus multilocularis. Echinococcus granulosus was not considered. Because histopathological findings such as outer acellular cuticular membrane, inner germinative membrane, and scolex required for the diagnosis of echinococcus granulosus were not available.[2] The medical history informed that the patient bred dogs since his childhood. The patient was started on albendazole 2 × 200 mg/day and was followed up. However, the patient did not come for control in the follow-ups. One year later, he presented to the emergency room with seizures. In the right frontal gyrus, the lesion, which was 6 mm in size before, was enlarged in the brain tomography, and the lesion was found to be 2.5 × 2 cm. He was operated on. Hydatid cyst was diagnosed again in the histopathological examination. The patient had used albendazole for a very short time and stopped the drug spontaneously. 20 days after the second operation contrast-enhanced CT examination of the patient’s upper/lower abdomen revealed a 13-cm thick-walled, cystic mass in the liver compatible with hydatid cyst with calcification on the wall. Contrast-enhanced thorax CT examination revealed multiple semisolid lesions consistent with hydatid cysts in both lungs, the largest of which was 3.2 cm. The patient was started on 2 × 400 mg/day albendazole. Two years have passed since the first diagnosis. Moreover, the patient did not come for 6 months.
Figure 2: Cuticle in eosinophilic appearance shows lamellation in necrotic tissue, granulation tissue in surrounding (a and b Hematoxylin and Eosin, x100)
Figure 3: Positive staining by using Grocott silver and PAS in the cuticle membrane (a and b ×100)
Alveolar Echinococcus (AE) is a zoonotic and parasitic disease of the genus Echinococcus, especially in the Northern Hemisphere (North America, Europe, parts of Africa, and South America, all of Asia except the southern part of Indonesia). Rodents and red fox are the main hosts for Echinococcus multilocularis, whereas the humans are the coincidental intermediate hosts.[3] After the transfer of the oncosphere to duodenum with the ingestion of the contaminated food, it traverses the intestinal wall and transported via the portal system to the liver where it is transformed into the metacestode. The metacestode may spread to the other organs by infiltration or metastasis and may manifest as a primary or secondary intracranial cyst.[4] Cerebral hydatid cysts account for 0.05% of all brain lesions in the developed countries; however, they account for 2.5-3.5% of all cerebral lesions in the endemic countries.[5] Hydatid cysts are usually acquired in childhood, and they become clinically manifest after a latent period of 5–15 years.[6] The diagnosis may be incidental as it was in our patient or the patients may present with the complaints of headache, vomiting, vision loss, or paresis according to the involved area in the brain.[6] As the number of the lesions was two, they were of solid character with heterogeneous contrast uptake and had peripheral edema; the preliminary diagnosis was made as a metastasis initially. As the red fox is common and hunted in Black Sea Region of our country, this may provide insight into why AE occurs at a higher rate in this geographical region. Our patient comes from Black Sea region of Turkey.
Hydatid cyst is a public health issue, requiring increased awareness especially in the endemic regions. Hydatid cysts can be misdiagnosed as tumors regardless of the organ involvement. An intracranial localization of the E. alveolaris cysts is quite uncommon in which a multidisciplinary approach is important in regard to the treatment and prognosis after the definite diagnosis.
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The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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