# Histopathological Features of Hepatocellular Carcinoma in Patients with Hepatitis B and D Virus Infection: A Single-Institution Study in Mongolia

## TL;DR

This study examines liver cancer in Mongolia, showing that hepatitis D virus co-infection with hepatitis B leads to more severe inflammation and suggests using CD4/CD8 cell markers to detect HDV in areas with limited testing.

## Contribution

The study identifies CD4/CD8 immunostaining as a potential diagnostic tool for HDV-related HCC in regions with limited HDV testing.

## Key findings

- HDV-positive HCC cases showed marked inflammation with CD4-positive T-cell infiltration in non-cancerous liver tissue.
- HDV-positive cells were spatially distinct from HBs antigen-positive cells, suggesting interference with HBV replication.
- CD4 and CD8 immunostaining can help detect HDV infection in areas where routine testing is rare.

## Abstract

Mongolia has a high prevalence of viral hepatitis, particularly hepatitis B virus (HBV), with an estimated 60% of HBV-infected individuals co-infected with hepatitis D virus (HDV), which accelerates liver disease progression. However, there is limited data on the contriburion of HDV infection to hepatocellular carcinoma (HCC) in Mongolia. This study clinicopathologically analyzed 49 HCC cases from the Mongolia–Japan Hospital between August 2020 and July 2024. Among these, 55.1% had HBV, and 28.6% were HDV-positive. Including the hepatitis C virus, a total of 75.5% of cases are viral hepatitis-related HCC. HDV-positive HCC cases showed marked inflammation in the non-cancerous liver tissue with infiltration of CD4-positive T-cells, with fewer CD8-positive cells. This study shows the current situation of HDV-related HCC in Mongolia and also suggests the usefulness of using CD4/CD8 immunostaining to determine HDV infection histologically in regions where routine testing for HDV is rare.

Background: Viral hepatitis, particularly hepatitis B (HBV) and hepatitis C (HCV), is highly prevalent in Mongolia. Moreover, Mongolia has the highest prevalence of hepatitis delta virus (HDV) globally, with over 60% of HBV-infected individuals also co-infected with HDV. Since HBV/HDV infections accelerate liver disease progression more compared to HBV infection alone, urgent national health measures are required. Method: This study presents a clinicopathological analysis of 49 hepatocellular carcinoma cases surgically resected at the Mongolia–Japan Hospital of the Mongolian National University of Medical Sciences. Results: HBV infection was found in 27 (55.1%) cases of all HCC cases. Immunohistochemical staining of the liver revealed that 14 (28.6%) cases were HDV antigen-positive in the HCC cases. HDV-positive cases exhibited significantly higher inflammatory activity compared to HDV-negative cases, with lymphocytic infiltrates predominantly composed of CD4-positive cells. Furthermore, HDV-positive cells were spatially distinct from HBs antigen-positive cells, suggesting that HDV-infected cells may interfere with HBV replication. No significant differences in fibrosis or in tumor characteristics were observed between the HDV-positive and negative cases. Early diagnosis of HBV/HDV infections is essential for appropriate treatment and to prevent further domestic transmission of the virus. However, routine testing for HDV infection is rarely conducted in Mongolia. Since HDV-positive cells are morphologically indistinguishable from surrounding HDV-negative cells, routine histopathological analysis may not be sufficient enough to detect HDV infection. Conclusions: Based on this clinicopathological study, CD4 and CD8 immunostaining can be considered an adjunctive diagnostic tool in cases with significant lymphocytic infiltration and hepatocellular damage. Additionally, HDV screening using blood and tissue samples may be recommended to ensure accurate diagnosis.