Description: Cyclin D1, one of the key cell cycle regulators, is a putative proto-oncogene overexpressed in a wide variety of human neoplasms. Cyclins are proteins that govern transitions through distinct phases of the cell cycle by regulating the activity of the cyclin-dependent kinases. In mid to late G1, Cyclin D1 shows maximum expression following growth factor stimulation. This antibody is useful for separating mantle cell lymphomas (Cyclin D1 positive) from SLL’s and small cleaved cell lymphomas (Cyclin D1 negative).