The bright structures seen in the image are most likely due to which of the following?

• A. Senile plaques
• B. Neurofibrillary tangles
• C. Lewy bodies
• D. Mitochondrial inclusions

Answer: (A)

Senile plaques are extracellular deposits of beta-amyloid that build up in the brain in Alzheimer’s disease. These amyloid plaques appear as bright, extracellular structures in histology images, especially when stained with amyloid-specific dyes like Congo red or thioflavin S, which highlight the beta-amyloid’s cross-beta sheet structure. This extracellular localization distinguishes them from other inclusions: neurofibrillary tangles are intracellular tau filaments within neurons, Lewy bodies are intraneuronal alpha-synuclein inclusions, and mitochondrial inclusions are not the hallmark extracellular plaques seen in Alzheimer’s. Therefore, the bright structures pictured are most consistent with senile plaques.