Department of Cellular Pathology, Royal Free Hospital, London, UK.
Division of Anatomic Pathology, Mayo Clinic, Rochester, MN, USA.
Division of Anatomic Pathology, Mayo Clinic, Rochester, MN, USA. Electronic address: firstname.lastname@example.org.
Hepatocellular carcinoma (HCC) is a common malignancy both in the United States of America and worldwide. Despite the refinement of imaging techniques in at- risk populations, a needle biopsy diagnosis remains an important diagnostic tool for HCC in many cases. Various immunohistochemical markers have been developed to facilitate this diagnosis, such as HepPar-1, glypican-3 and, most recently, arginase-1. Amongst them, arginase-1 has been shown to have superior sensitivity and specificity than the others. Performance of arginase-1 has been reported to be excellent for diagnosis of well differentiated HCCs, with some tail- off in sensitivity for poorly differentiated tumors. Our experience has suggested that a subset of well differentiated HCCs can be negative for arginase-1. We examined 68 consecutive confirmed cases of well differentiated HCC diagnosed on needle biopsy, and found 7 (10%) to be completely negative for arginase-1. This finding is of fundamental clinical importance in view of previous studies that have shown arginase-1 to be always positive in well differentiated HCC.