RESUMO
BACKGROUND: Echinococcus is a worldwide zoonosis, primarily causing liver lesions. Accidentally detected, these lesions enter the differential diagnosis of a tumor, including metastasis. This situation is especially challenging in patients with colorectal cancer, as both diseases affect mainly the liver. CASE PRESENTATION: We report two patients with a newly diagnosed colorectal cancer. Pre- and intraoperatively radiological imaging revealed hepatic lesions which were resected on suspicion of colorectal cancer metastasis. Histology showed granulomatous lesions with characteristic parasitic membrane consistent with an echinococcal cyst. The diagnosis was confirmed by specific polymerase chain reaction. CONCLUSIONS: Focal hypoechoic liver lesion in patients with colorectal cancer should be primarily considered as a liver metastasis and resected whenever feasible. Other uncommon etiologies, including parasitic lesion as echinococcal cysts, should be taken in consideration, as this could lead to major changes of the management and prognosis of the affected patients.