Air-dried smears for optimal diagnostic immunocytochemistry

Abstract

Objective: To exploit formalin-postfixed, air-dried smears for diagnostic immunocytochemistry (ICC).

Study design: A series of 144 cases of diagnostic fine needle cytology samples in which air-dried, supplementary smears were available was used to exploit postfixation in the process of antigenic stabilization and rescue for immunocytochemical staining.

Results: Postfixation with formalin and with a formalin/ethanol solution gave comparable results as far as recovery and immunocytochemical detection of most monoclonal and polyclonal antibodies. The visualization of the antibody reactions was often superior to that obtained with wet-fixed slides, probably due to the interaction of slow cell dehydration with their consequent optimal flattening observed with formalin postfixation after short rehydration in physiologic saline.

Conclusion: Although wet fixation of cytopathologic slides in 95% ethanol represents a common standard for ICC, the usage of formalin-postfixed air-dried smears proved reliable and efficient for antigenic rescue and may enter routine usage in cytopathology laboratories. Moreover, in some instances, the visual evaluation of results was easier in the larger, well-flattened cells obtained in air-dried cells.