Clusterin antibody, also known as Apo lipoprotein J, has been implicated in numerous processes including active cell death. Clusterin is expressed in normal brain and has been reported to be overexpressed in anaplastic large cell lymphoma (ALCL) and in pancreatic, breast, prostate and ovarian cancers. Clusterin has been shown to stain 95% of systemic ALCL, including 100% of ALK-1(+) and 91% of ALK-1(-) ALCL. Studies have shown that clusterin may be a useful diagnostic marker for ALCL, especially in ALK-1(-) cases. Overexpression of clusterin appears to be a useful prognostic factor for patients with ovarian carcinomas.