Use of destained cytology slides for the application of routine special stains

Abstract

Background: Special stains to demonstrate microorganisms or intra- and extracellular substances have not been evaluated in detail regarding their applicability and usefulness in destained cytologic specimens.

Objectives: The aim of this study is to compare the results of routine special stains on destained slides previously stained with Hemacolor and on fresh (unstained) specimens.

Methods: Archival Hemacolor-stained fine needle aspirate specimens of inflammation with infectious agents (bacterial, mycobacterial, and fungal infections), neoplasia (melanoma, myxosarcoma, and mammary adenocarcinoma), and hemorrhage (pericardial effusion) from 14 dogs and 7 cats were selected. Cells in a minimum of 4 fields were photographed and 5 slides from each case were then destained by different methods (alcohol acid or microwave). Seven special stains were applied selectively to the destained slides, depending on the cytologic findings: periodic acid Schiff, Grocott-Gomori methenamine silver, Gram's, Ziehl-Neelsen, Alcian blue, Fontana-Masson, and Prussian blue. The same fields were rephotographed and 2 observers evaluated the slides qualitatively, with comparison to fresh cytologic specimens from similar lesions.

Results: Special stains applied to destained slides demonstrated the expected cellular and extracellular material or organisms independent of the destaining method. Staining intensity, nonspecific staining (background), cell morphology, and nuclear counterstaining results were similar to those of special stains applied to fresh unstained slides.

Conclusions: Destaining does not appear to affect the results of routine special staining for cytologic specimens. Destaining before special stains may be a valuable diagnostic strategy when few slides are present or only stained slides are available.