Positron emission tomography-computed tomography (PET/CT) improves the diagnostic interpretation of fluorine-18 fluorodeoxyglucose (18F-FDG ) PET and CT in oncologic patients and has an impact on both diagnostic and therapeutic aspects of patient management. However, false positive findings from the PET/CT imaging should be taken into consideration as they mislead physicians into improper therapeutic actions. We present a 48-year-old female patient with a history of left colectomy for colorectal cancer and subsequent liver metastasectomy. After one year of follow-up, she presented with a highly suspicious lesion in the liver, which was confirmed on PET/CT as a metastatic liver tumor. Consequently, the patient underwent surgical excision of the tumor, and the definitive histological diagnosis showed a granulomatous tissue with giant cells and foreign body tissue reaction. Based on this report, we briefly review the dangerous pitfalls from radiological and PET/CT imaging concerning the preoperative diagnostic workup examination, as they may significantly alter the treatment plan in oncologic patients.