Background: Hepatocellular carcinoma (HCC) is the most prevalent primary hepatic neoplasm, with approximately 50% of cases eventually developing metastasis. HCC metastasis to the pelvis is exceedingly rare due to the significant anatomical distance and intricate metastatic pathways involved. Case presentation: In this case report, we present a 60-year-old male with HCC metastasis to the pelvis that had infiltrated the rectum. Initially, we suspected the pelvic mass to be a GIST, but histopathological and immunohistochemical examinations revealed it to be HCC metastasis. The dissemination of the tumor was suspected to have occurred through peritoneal implantation following an RFA procedure that the patient had undergone ten months prior. A resection surgery of the sigmoid colon up to the tumor-free mid-rectum was performed. The patient is currently stable and undergoing routine outpatient care, now in the third-month post-surgery. Conclusion: This case report unveils a rare HCC metastasis to the pelvis with rectal infiltration. We conclude that in HCC patients presenting with obstructive symptoms, suspicion of metastasis to the pelvis should be considered, especially in patients who have undergone an RFA procedure. Limited diagnostic support from CT scans and colonoscopy made establishing a definitive diagnosis before surgery challenging. However, patients can attain a favorable prognosis with effective surgical intervention, underscoring the importance of prompt and effective treatment in such cases.

Keywords: Carcinoma, Hepatocellular; Neoplasm Metastasis; Pelvis; Rectum; Case Reports.