Simple protocol for DNA extraction from archival stained FNA smears, cytospins, and thin preparations

A high proportion of patients with lung carcinoma present at a late stage of disease or have significant comorbidities which preclude treatment by aggressive surgical approaches. Consequently, many of these patients must be diagnosed and treated based on the assessment of cytologic samples or very small biopsies. Molecular testing, now an integral part of this assessment, introduces an additional level of complexity in the triaging of limited tissue for maximal diagnostic yield. Archived and previously stained cytologic samples provide a robust source of material for molecular studies. However, optimal techniques of tissue retrieval and DNA extraction are crucial to maximize the DNA yield. In this communication, we outline our protocol for obtaining DNA from archival cytologic material. The method is simple, requires no destaining steps or extensive manipulation of the sample, and yields sufficient DNA for the standard performance of routine molecular studies.