Diagnostic utility of hepatocyte paraffin-1 immunohistochemistry on cell blocks in differentiating hepatocellular carcinoma from metastatic liver cancers in low resource settings

Background: Liver cancers are primarily metastatic, often originating from gastrointestinal adenocarcinomas. Among primary liver cancers, hepatocellular carcinoma (HCC) accounts for approximately 80% of cases and ranks sixth globally in incidence and third in cancer-related mortality. In Tanzania, HCC is the 8 ^th most common malignancy and the 5 ^th leading cause of cancer deaths. Diagnosis typically involves triple-phase CT scan, core needle biopsies, or laparotomies, but these are expensive and invasive or often inaccessible in low-income settings. Ultrasound-guided fine needle aspiration biopsy (FNAB) presents a more accessible, cost-effective, and less invasive alternative. However, FNAB alone struggles to distinguish poorly differentiated HCC from metastatic liver cancers. Hepatocyte paraffin-1 (Hep Par 1) immunohistochemistry (IHC) on cell blocks offers high diagnostic accuracy, with nearly 100% sensitivity and specificity, but its use is limited in low- and middle-income countries. Materials and methods: This hospital-based prospective cross-sectional study aimed to evaluate the diagnostic value of Hep Par 1 IHC on cell blocks in differentiating HCC from metastatic cancers in a resource-limited setting. Over one year, 55 patients with suspected liver cancer were enrolled, with 50 meeting the inclusion criteria. FNAB samples were used for both conventional smears and cell block preparations, followed by Hep Par 1 IHC. Results: Findings showed FNAC identified only 10% of cases as HCC, whereas cell blocks and IHC identified 56% and 66%, respectively. Conventional cytology alone misclassified 46% of cases as metastatic. Its agreement with IHC was low (41.7%, Kappa = 0.1), whereas cell blocks showed high concordance (79.17%, Kappa = 0.61). Conclusion : The study concludes that while FNAB remains vital in low-resource settings for the diagnosis of HCC, relying on it alone leads to significant diagnostic errors. It recommends integrating cell blocks and Hep Par 1 IHC into routine diagnostics to improve accuracy and reduce misdiagnosis in Tanzania and similar contexts.