Unusual extrahepatic metastatic site of hepatocellular carcinoma with post-therapy disseminating metastases presenting as a primary soft tissue sarcoma: case report.

Introduction and importance: Hepatocellular carcinoma (HCC) is a highly malignant primary hepatic tumor. However, extrahepatic metastatic sites of HCC with post-therapy dissemination of metastases mimicking primary soft tissue sarcomas with rib metastases are extremely rare. Case presentation: The authors report a unique case of hepatitis B virus (HBV)-positive HCC with bilateral lung involvement and widespread right-flank soft tissue and rib metastases. The pathological diagnosis after surgical resection confirmed extrahepatic HCC metastasis. Subsequently, adjuvant-targeted and immune-checkpoint inhibitor therapies were still initiated. Clinical discussion: Extrahepatic HCC metastasis, which initially presents at distant sites, is uncommon. HCC commonly metastasizes to the lungs, bones, lymph nodes, kidneys, adrenal glands, and peritoneum/omentum. HCC with aggressive post-scheduled adjuvant therapy to the lungs and hypochondriac soft tissue with rib metastasis is very rare and has a poor prognosis. Conclusion: Although most patients with HCC have disseminated extrahepatic metastases, primary HCC should still be treated. Thus, a review of the history and imaging, histopathology, and immunohistochemical findings is crucial for the definite and differential diagnosis of this tumor.