Patterns and Clinicopathological Features of Histologically Proven Metastases in Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is the most common primary liver malignant neoplasm. Multiple risk factors have been identified for several decades for this overly aggressive tumor. HCC is an overly aggressive malignancy with frequent intrahepatic and extrahepatic metastasis. In our practice, we have observed that HCC has the propensity to metastasize to very unusual sites and can sometimes show variable patterns leading to diagnostic difficulty. In this study of 257 patients, we aim to discuss the unusual sites of HCC metastasis, the various patterns of metastasis, clinicopathological features, and the most common cause of HCC in our population. In the course of our research study, we systematically extracted a comprehensive dataset comprising 257 instances of metastatic HCCs from the hospital database spanning the period from 2016 to February 2022. The assessment of metastatic sites uncovered a wide range of locations, reflecting significant diversity. The most common location was bone, with 135 cases (52.5%). The vertebral column was the most common location among bony metastasis, with 63 cases (24.7%). Morphologically, the most common histological pattern observed was pure trabecular in 192 patients (74.7%). All cases were diagnosed with the help of immunohistochemical stains. Out of 257 cases, 29.18% were diagnosed using glypican-3 and HepPar1, while 26.1% relied solely on HepPar1 positivity. HepPar1 was performed in a total of 240 cases, and positivity was seen in 205 cases (85.5%). In summary, our study represents the most comprehensive investigation of clinicopathological characteristics in metastatic HCC conducted within the past 20 years. It helps understand the histological and immunohistochemical features useful for diagnosis at metastatic sites for tumors with an unknown primary.