Hepatic Angiomyolipomas May Overexpress TFE3, but Have No Relevant Genetic Alterations

The fusion or amplification of TFE3 has been identified as one of the molecular events underlying tumorigenesis in perivascular epithelioid cell tumors (PEComas). TFE3 rearrangements in PEComas are related to the morphological features of the epithelioid appearance and weaker expression of immunohistochemical muscular markers. This study aimed to clarify whether these genetic alterations are involved in hepatic angiomyolipomas (AMLs), which are a member of the PEComa tumor family. We examined 28 liver specimens (15 biopsies and 13 surgical specimens) of hepatic AMLs obtained from 26 patients. Renal AMLs (n=20), extrahepatorenal PEComas (n=3), lymphangiomyomatosis (n=8), and hepatocellular carcinomas (n=40) were used as a control. A histologic comparison between hepatic and renal AMLs revealed that the epithelioid appearance was more common in hepatic tumors (38% versus 0%, P=.006). In immunohistochemistry, the expression of HMB45 and Melan-A appeared to be more widespread in hepatic AMLs than in renal AMLs, whereas smooth muscle actin and desmin were less broadly expressed in hepatic tumors (all P<.001). TFE3 also appeared to be overexpressed in 6 (21%) of 26 hepatic AMLs and 3 (100%) of 3 PEComas, but in none of the renal AMLs. In fluorescence in situ hybridization, although all PEComas harbored a TFE3 rearrangement or amplification, no genetic alterations were found in any hepatic AMLs. In conclusion, although hepatic AMLs and TFE3-rearranged PEComas share pathological features such as the epithelioid appearance and immunoreactivity to TFE3, TFE3 alterations are less likely to be a major molecular event driving tumorigenesis in hepatic AMLs.