Progress in pathologyImmunohistochemical approach for the diagnosis of a liver mass on small biopsy specimens

- HCC shares overlapping histological features with benign hepatocellular lesions.
- Metastatic tumors can be indistinguishable from HCC on histologic grounds.
- IHC markers play an important role in establishing an accurate diagnosis.

SummaryWell-differentiated hepatocellular carcinoma (HCC) shares overlapping histological features with benign hepatocellular lesions, including hepatocellular adenoma and focal nodular hyperplasia in non-cirrhotic liver, and with high-grade dysplastic nodule in cirrhotic liver. Several metastatic tumors, such as neuroendocrine tumor, renal cell carcinoma, adrenocortical carcinoma, melanoma, and epithelioid angiomyolipoma, can be indistinguishable from HCC on histologic grounds. Since this distinction has important therapeutic implications, judicious use of immunohistochemical markers plays an important role in establishing an accurate diagnosis, especially when limited material of tumor is available on cell block or a small core biopsy. This review describes commonly used immunohistochemical markers used in the diagnosis of HCC, highlighting advantages and disadvantages of each marker, and suggests appropriate immunohistochemical panels for specific clinicopathologic situations.