Background: The diagnosis of primary liver carcinoma (PLC) primarily relies on routine histopathology with hematoxylin and eosin (H&E) and the supportive evidence of immunohistochemistry (IHC). Inappropriate use of immunostains without either careful histomorphological evaluation or clinical correlation may lead to misdiagnosis and inappropriate patient management.

Objective: To retrospectively analyze the interpretation pitfalls in IHC as an adjunct in assessing PLCs in liver biopsy specimens at a tertiary hospital in Thailand.

Materials and Methods: The archives of the Division of Pathology, Thammasat University Hospital, were searched between 2015 and 2020 using a search tool from the pathology software system and a combination of codewords, including PLC, hepatocellular carcinoma (HCC), and intrahepatic cholangiocarcinoma (iCCA). Histomorphology of PLCs in liver biopsy specimens and the corresponding immunophenotypes were retrospectively analyzed. Clinical data for each patient was retrieved from the electronic medical record.

Results: One hundred fifty-three liver biopsy specimens were retrieved. There were 128 (83.7%) iCCA, 23 (15%) HCC, and 2 (1.3%) combined hepatocellular-cholangiocarcinoma (cHCC-CCA). Six cases (3.9%) with interpretation pitfalls in IHC were analyzed. These pitfalls included incorrect subtyping of PLCs in two cases (1.3%) and PLCs misdiagnosed as metastatic cancers in four cases (2.6%).

Conclusion: Interpretation pitfalls in IHC of PLCs were noted in 3.9% of the present study cohorts. Pathologists should be familiar with the histomorphology of PLCs together with their rare variants. Appropriate use of IHC as adjuncts for evaluating PLCs and correlation with clinical details were essential for rendering the correct diagnoses of PLCs.

Keywords: Immunohistochemistry; Primary liver carcinoma; Interpretation

DOI: 10.35755/jmedassocthai.2022.05.12421

Received 1 March 2021 | Revised 7 April 2022 | Accepted 8 April 2022