Differential diagnosis of liver lesion in the absence of proven primary tumor is still a challenge. We experienced a case of an asymptomatic 14 cm lesion of right hemiliver in a 67 year-old man submitted to right hepatectomy in December 2010. One year before the patient underwent to endoscopic removal of a tubular adenoma of the right colon. Preoperative diagnosis was supported by ultrasound, CT scan, PET and liver biopsy. The patient received 6 cycles of preoperative chemotherapy (FOLFOX) with down-staging of the lesion diameter. Immunohistochemistry on the surgical specimen showed positivity for cytokeratins 19 and 20, CEA, MUC-2, negativity for cytokeratin 7 and a-fetoprotein. Moreover, the neoplastic cells showed a focal positivity with lower intensity for MUC-1 and MUC-5AC. The immunohistochemical profile suggested the possibility of a metastatic tumour from the large bowel, without excluding a primitive mucinous cholangiocarcinoma with intestinal phenotype. At 6 months after intervention, the patient was submitted to chemotherapy (FOLFOX). At present he is in good condition, without radiological signs of recurrence. Oncologists must evaluate the possible benefits of further adjuvant treatments based on the differential diagnosis between a primitive or metastatic liver tumour. In conclusion, correct diagnosis of liver masses is mandatory and remains a challenge that can differentiate either follow-up or surgical and adjuvant treatment. Histology and immunohistochemistry must be related to clinical findings as they may not always be sufficient to reach a correct final diagnosis, and can even be confusing. At present, molecular biology cannot be considered a helpful for diagnosis in these cases.