Immunomorphology and molecular biology of mixed primary liver cancers: is Nestin a marker of intermediate-cell carcinoma?

Aims: Primary mixed liver cancers (PLCs), combined hepatocellular-cholangiocellular (cHCC-CC) and intermediate-cell carcinomas are rare tumours characterised by different molecular mechanisms. Nestin is a marker of progenitor cells with a promising application in human tumours. The aims of the present paper are (i) to determine the expression of Nestin in mixed PLCs; and (ii) to correlate the PLC immunoprofile with the gene expression in each tumour component. Methods and results: We selected 28 mixed PLCs, 13 (46.4%) cHCC-CC and 15 (53.6%) intermediate-cell carcinomas. The immunohistochemistry panel consisted of keratin 7, keratin 19, CD56 and Nestin. Next-generation sequencing analysis was performed on 17 cases (27 specimens) using a multi-gene custom panel. The differentiated HCC and CC components of cHCC-CC were negative for Nestin in all cases. The intermediate areas of cHCC-CC were immunoreactive for Nestin in 92.3% of cases, for CD56 in 76.9% and for K7/K19 in all cases. The immunoprofile of the intermediate-cell carcinomas showed 73.3% of cases positive for Nestin and 66.7% for CD56. TP53 and TERT were the most frequently mutated genes (31.3% and 17.6% of samples, respectively). Mutations were also found in IDH1, IDH2, PIK3CA and NRAS genes. Intermediate and HCC areas of cHCC-CC seemed to share the same mutational profile, and both harboured different mutations than the CC component. Conclusions: According to our preliminary data, Nestin was not expressed by hepatocellular or cholangiocellular-cell components, but was expressed by most of the intermediate cells in PLCs, and therefore could be considered in the differential diagnosis of PLCs, together with mutational profile.