The Bcl-2 family of proteins regulates apoptosis by controlling mitochondrial permeability and release of cytochrome c. Bcl-2 is an anti-apoptotic protein that resides in the outer mitochondrial wall and inhibits release of cytochrome c. Over-expression of Bcl-2 has been shown to promote cell survival by suppressing apoptosis. It has been documented that Bcl-2 becomes deregulated in tumor cells as a result of translocation into the immunoglobulin heavy-chain locus and is therefore activated in B-cell malignancies. Bcl-2 is useful in differentiation of follicular lymphoma from reactive follicular proliferation (Bcl-2 negative). In addition, Bcl-2 has been shown to be correlated with disease prognosis in breast cancer, prostate cancer, ovarian cancer, endometrial cancer and colon cancer.