Cytopathology smears from autopsies: A viable storage method for molecular analysis

Cytology appears to be a viable option to histological samples for proper storage and maintenance of autopsy material for DNA extraction and analysis. In the present study, we tested the feasibility of using archived air-dried smears produced at the time of the autopsy for simple molecular analysis, comparing quantity and quality of the DNA extracted from the smears to that of correspondent histological specimens.

Air-dried cytological smears were obtained from scrapings of exactly the same areas collected for histological study. DNA was extracted using a commercially available protocol from all samples, with calculation of purity ratio and overall concentration. The integrity of the extracted DNA was also verified through conventional polymerase chain reaction (PCR).

Five cases of lung tumours (2 small cell carcinomas and 3 adenocarcinomas) were collected. Percentage of tumour cells and necrosis ranged from 30% to 90% and from 10% to 40%, respectively, in the cytological preparations, and from 50% to 90% and from 10% to 80%, respectively, in the histological preparations. Purity ratio (260/280) had a median of 1.87 in cytology vs 1.94 in histology. Mean DNA concentration among the cytological preparations was 2653 ng/mL (range 1684-3980 ng/mL) vs 757.2 ng/mL among the histological preparations (range 456-1829 ng/mL. DNA from all five cases of cytology was successfully amplified by conventional PCR, in contrast to none from the histology specimens.

Archived air-dried smears scraped from tumoural lesions in autopsies have proven to yield a good concentration of quality DNA for conventional PCR, with better results than formalin-fixed paraffin embedded material.