Azzopardi phenomenon

The Azzopardi phenomenon, or Azzopardi effect, is the presence of DNA in necrotic venules.^[1] It can occur in small cell carcinomas and in some high-grade malignant neoplasms.^[1][2] The effect is well known in diagnostic surgical pathology.^[3] The phenomenon is named after the pathologist, John G. Azzopardi.^[4][5][6]

Azzopardi was able to correctly characterize the effect as due to DNA; it had been thought previously but incorrectly to be calcium.^[4] Necrosis results in the release of cellular DNA, which adheres in patches to the walls of blood vessels, showing as intensely basophilic material on hematoxylin-eosin stain.^[1]