ESM1 as a Marker of Macrotrabecular-Massive Hepatocellular Carcinoma

Purpose: Macrotrabecular-massive hepatocellular carcinoma (MTM-HCC) is a novel morphological subtype of HCC associated with early relapse after resection or percutaneous ablation, independently of classical clinical and radiological prognostic factors. The aim of the present study was to identify immunohistochemical markers of MTM-HCC, to ease its diagnosis and implementation into clinical practice. Experimental Design: To identify potential biomarkers of MTM-HCC, we first analyzed gene expression profiling data from The Cancer Genome Atlas study and further selected two candidate biomarkers. Performance of both biomarkers for diagnosis of MTM-HCC was further tested by immunohistochemistry in two independent series of 67 and 132 HCC biopsy samples. Results: Analysis of RNA sequencing data showed that MTM-HCC was characterized by a high expression of neoangiogenesis-related genes. Two candidate biomarkers, Endothelial-Specific Molecule 1 (ESM1) and Carbonic Anhydrase IX (CAIX), were selected. In the discovery series, sensitivity and specificity of ESM1 expression by stromal endothelial cells for the detection of MTM-HCC were 97% (28/29), and 92% (35/38), respectively. Sensitivity and specificity of CAIX were 48% (14/29) and 89% (34/38). In the validation set, sensitivity and specificity of ESM1 for the identification of MTM-HCC were 93% (14/15) and 91% (107/117), respectively. Interobserver agreement for ESM1 assessment was good in both series (Cohen Kappa 0.77 and 0.76). Conclusions: Using a molecular-driven selection of biomarkers, we identified ESM1 as a reliable microenvironment immunohistochemical marker of MTM-HCC. The results represent a step toward the implementation of HCC morpho-molecular subtyping into clinical practice.