Immunohistochemical markers on needle biopsies are helpful for the diagnosis of focal nodular hyperplasia and hepatocellular adenoma subtypes.

Phenotypic identification of focal nodular hyperplasia (FNH) and hepatocellular adenoma (HCA) subtypes using immunohistochemical markers has been developed from their molecular characteristics. Our objective was to evaluate the sensitivity of these markers in the definitive diagnosis of these lesions by core needle biopsies. A total of 239 needle biopsies paired with their surgical resection specimen (group A) or without an associated resection specimen (group B) were reviewed. Using a step-by-step algorithm after standard staining, appropriate immunostaining analyses were performed to determine the certainty of diagnosis of FNH, HNF1α-inactivated HCA, inflammatory HCA, β-catenin-activated HCA, or unclassified HCA. The diagnosis of FNH was certain or probable on routine stains in 53% of needle biopsies of group A, whereas after glutamine synthetase staining, the diagnosis was certain in 86.7% as compared with 100% on the corresponding surgical specimen (P=0.04). In needle biopsies of group A, the diagnosis of HCA was certain on routine stains in 58.6% as compared with 94.3% on surgical specimens. After specific immunostaining, diagnosis was established on biopsies with 74.3% certainty, including all HCA subtypes, with similar distribution in surgical specimens. For each "certain diagnosis" paired diagnostic test (biopsy and surgical specimen), a positive correlation was observed (P<0.001). No significant difference was observed between groups A and B for FNH (P=0.714) or for HCA subtypes (P=0.750). Compared with surgical specimens, immunohistochemical analysis performed on biopsies allowed the discrimination of FNH from HCA and the identification of HCA subtypes with good performance.