The central structure in this image is associated with Alzheimer's disease. Which structure is it most likely?

• A. Senile plaque
• B. Neurofibrillary tangle
• C. Lewy body
• D. Pick body

Answer: (A)

Alzheimer disease features include extracellular beta-amyloid plaques that appear as dense core deposits with a surrounding halo. If the image shows a conspicuous extracellular deposit with a dense central core, that matches a senile (amyloid) plaque. Neurofibrillary tangles are intracellular twisted filaments of hyperphosphorylated tau inside neurons; Lewy bodies are alpha-synuclein inclusions; Pick bodies are tau-positive inclusions seen in frontotemporal dementia. So the structure shown is most consistent with a senile plaque.