Which is the pathognomic feature of Alzheimer’s disease?
Ref. Robbins Pathology. 9th edition. Page. 1289
 

Grossly, brain atrophy (narrowed gyri and widened sulci) is predominant in the frontal and superior temporal lobes.
Alzheimer microscopically characterized by numerous neuro brillary tangles and senile plaques with a central core of amyloid alpha protein
Silver stains demonstrate tangles and plaques and Congo red shows amyloid deposition in plaques and vascular walls (amyloid angiopathy).
There are also numerous Hirano bodies, and granulovacuolar degeneration is found in more than 10 of the neurons of the hippocampus.
Lewy bodies
Ballooned neurons
Plaques and tangles
Pick bodies