Serum Amyloid A (SAA) is an acute-phase protein primarily synthesized in the liver. While it is typically found at low concentrations in healthy individuals, pro-inflammatory cytokines upregulate SAA production to encourage recruitment of immune cells to inflammatory sites.

Amyloidosis is a disease characterized by the abnormal build-up of amyloid, abnormal non-branching fibrillary β-pleated sheet proteins that are insoluble and highly resistant to proteolytic degradation that result in localized or systemic organ dysfunction. Amyloidoses are grouped as AL (primary), AA (secondary), and hereditary forms. Proper classification is important since treatment and prognoses of the disorders are vastly different. AA amyloidosis is associated with a variety of chronic inflammatory conditions and infections, derived from SAA. Immunohistochemical staining using a panel of antibodies including κ and λ Ig light chains, amyloid A, and transthyretin can aid in recognizing most forms of amyloid.

Recently, SAA has also been investigated as a potential marker for neoplastic activity. SAA concentrations have been reported to be a marker of poor prognosis, elevated in patients with advanced stages of cancer and those with malignant disease.