Immunohistochemical expression of manganese superoxide dismutase in hepatocellular carcinoma, using a specific monoclonal antibody

The expression of manganese superoxide dismutase (Mn-SOD) was studied immunohistochemically, using a specific monoclonal antibody, in surgically resected hepatocellular carcinoma (HCC) and noncancerous tissues from 47 patients (2 with well-differentiated HCC, 36 with moderately differentiated HCC, 8 with poorly differentiated HCC, and 1 with undifferentiated carcinoma). Cancer cells in 44 patients (93.6%) were positive for Mn-SOD. The staining pattern of cancer cells was mostly homogeneous in well-differentiated HCC, whereas it was heterogeneous in poorly differentiated HCC. Moreover, strongly positive immunoreactivity was observed in noncancerous liver tissues in all patients, especially in normal hepatocytes surrounding HCC, regenerative small hepatocytes in the tumor boundary, and mononuclear inflammatory cells in the necroinflammatory lesions. The positive immunoreactivity for Mn-SOD in patients with HCC appears to reflect increased production of the enzyme protein.