Cytomorphologic manifestations of Alzheimer's disease using brain squash smears: An autopsy study with histology-cytology correlation

Alzheimer's disease (AD) is the most common form of dementia. The cardinal histopathologic features include senile plaques (SPs) and neurofibrillary tangles (NFTs), and in addition, granulovacuolar degeneration (GVD) and Hirano bodies (HBs) are frequently observed in the hippocampus. We studied hippocampal cytological features of AD, compared with controls. Hippocampal squash smears were prepared from 26 autopsy brains and stained with three different solutions, including Papanicolaou stain (Pap-s). The smears were evaluated for the aforementioned four structures and gliosis, and their frequency was compared between AD (n = 15) and control (n = 11) groups. Hippocampal smears of all AD cases revealed NFTs and gliosis. NFTs were light gray with thick flame-like structures on Pap-s. GVD was identified in the majority of AD cases and was most easily observed on Pap-s. SPs were difficult to identify and were seen only in AD cases. HBs were rarely identified as long light eosinophilic hyaline structures on Pap-s. Cytological findings of hippocampi reflect the characteristic histological features of AD with the exception of HBs, which are difficult to identify on smears. NFTs and gliosis, and SPs seem to be sensitive and specific cytologic markers in hippocampal smears for AD, respectively.