Alzheimer's Disease; cerebrovascular amyloid: Congophilic or amyloid angiopathy is the result of deposition of beta amyloid within small cerebral arteries and arterioles. In this congo red stained section under polarized light, the amyloid in several vessels is demonstrated by its typical green birefringence. The DNA sequence for the amyloid precursor protein has been mapped to the long arm of chromosome 21.