Annexin 1

Annexin-1 (A1) was identified by gene expression profiling studies of hairy cell leukemia. In the appropriate context, positivity for annexin A1 favors a diagnosis of hairy cell leukemia. Normal granulocytes and precursors also express annexin A1, serving as a positive internal control in bone marrow specimens. Hairy cell leukemia is a low-grade B-cell lymphoid neoplasm with distinct clinical features, including a high frequency of marked splenomegaly and a relatively small number of circulating neoplastic cells in the peripheral blood. Accurate diagnosis of hairy cell leukemia is important, since patients tend to respond well to interferon and purine analogues, unlike other low-grade B-cell lymphoproliferative disorders. In most cases, a diagnosis of hairy cell leukemia can be confidently established based on morphologic and immunohistochemical analysis. However, in some situations distinction from other low-grade B-cell lymphomas can be difficult. One tumor that may be particularly difficult to distinguish from hairy cell leukemia is marginal zone B-cell lymphoma (particularly the variant referred to as "splenic lymphoma with villous lymphocytes"). Immunohistochemical marker, Annexin A1, that appears to hold great promise for diagnosing hairy cell leukemia and distinguishing it from mimics. They identified a group of 89 genes that were either upregulated or downregulated in patients with hairy cell leukemia. Annexin A1 (ANXA1), a gene related to phagocytosis, was found to be one of the most highly upregulated genes in hairy cell leukemia. Based on this information, the investigators hypothesized that immunostaining using a monoclonal antibody directed against the Annexin A1 gene product may prove useful in the diagnosis of hairy cell leukemia.

No special preparation is needed for Annexin 1. Inform your doctor if you are on any medications or have any underlying medical conditions or allergies before undergoing Annexin 1. Your doctor depending on your condition will give specific instructions.