Immunohistochemical testing for Hep Par-1 (Hepatocyte Paraffin 1) aims to detect an antigen present in the mitochondria of both normal and cancerous liver cells (hepatocytes). It is a highly sensitive and specific marker of hepatocyte origin, making it an essential tool in confirming the diagnosis of hepatocellular carcinoma (HCC) and differentiating it from other tumors, particularly metastatic cancers to the liver.