Case Report: A hepatic lesion is not always metastasis: synchronous rectal adenocarcinoma and primary hepatocellular carcinoma followed by a benign necrotic liver nodule.

Background: Liver lesions identified during postoperative surveillance of colorectal cancer are commonly presumed to represent colorectal liver metastases. However, patients with chronic liver disease may develop additional primary hepatic malignancies, creating significant diagnostic and therapeutic challenges. We report a rare case of rectal adenocarcinoma followed by pathologically confirmed primary HCC and a subsequent benign hepatic necrotic nodule, both initially suspected to represent metastatic or recurrent disease. Case description: A 56-year-old man with a 20-year history of chronic hepatitis B was diagnosed with rectal adenocarcinoma and underwent laparoscopic Low Anterior Resection. Seven months later, a solitary hepatic lesion was identified during surveillance. Although colorectal liver metastasis was initially suspected, elevated alpha-fetoprotein levels and characteristic imaging findings suggested primary HCC. Right hepatectomy confirmed moderately to poorly differentiated HCC with microvascular invasion. Five months after adjuvant transarterial chemoembolization, another hepatic lesion was detected and considered highly suspicious for recurrence. Repeat resection was performed, but pathology revealed only necrosis and fibrosis without viable tumor cells, confirming a benign necrotic hepatic nodule. No recurrence or metastasis was observed during follow-up. Conclusion: This case highlights the diagnostic complexity of hepatic lesions arising in patients with colorectal cancer and chronic hepatitis B infection. Not all hepatic lesions represent metastatic disease, and accurate diagnosis requires integration of clinical history, imaging findings, tumor biomarkers, and histopathological confirmation.