Evaluation of a method for cryogenic storage of cytological specimens.

A technique for long-term storage of cytological specimens at -70 degrees C was evaluated with a range of nongynaecological cytology specimens. The effects of frozen storage on the cellularity, morphology, ultrastructure, and reactivity to cytochemical and immunochemical stains were investigated. These parameters were compared in preparations made from specimens processed conventionally and after frozen storage. No significant deterioration in the quality of subsequent preparations was apparent after storage. The method is technically simple and has proven successful for storing a range of specimens, including serous effusions, urine samples, and fine-needle aspirates. This technique allows storage of material until initial microscopic evaluation is complete. If required, the relevant adjuvant procedure, such as cell blocking, may then be carried out using the stored material. Wastage of cytological material on unnecessary preparations is minimised, and material may be stored over years for research or confirmation procedures.