Buffered Romanowsky-Giemsa method for formalin fixed, paraffin embedded sections: taming a traditional stain.

Romanowsky-Giemsa (RG) stains were devised during the 19th century for identifying plasmodia parasites in blood smears. Later, RG stains became standard procedures for hematology and cytology. Numerous attempts have been made to apply RG staining to formalin-fixed paraffin-embedded tissue sections, with varied success. Most published work on this topic described RG staining methods in which sections were overstained, then subjected to acid differentiation; unfortunately, the differentiation step often caused inconsistent staining outcomes. If staining is performed under optimal conditions with control of dye concentration, pH, solution temperature and staining time, no differentiation is required. We used RG and 0.002 M buffer, pH 42, for staining and washing sections. All steps were performed at room temperature. After staining and air drying, sections were washed in 96-100% ethanol to remove extraneous stain. Finally, sections were washed in xylene and mounted using DPX. Staining results were similar to routine hemalum and eosin (H & E) staining. Nuclei were blue; intensity depended largely on chromatin density. RNA-rich sites were purple. Collagen fibers, keratin, muscle cells, erythrocytes and white matter of the central nervous system were stained pinkish and reddish hues. Cartilage matrix, mast cell granules and areas of myxomatous degeneration were purple. Sulfate-rich mucins were stained pale blue, while those lacking sulfate groups were unstained. Deposits of hemosiderin, lipofuscin and melanin were greenish, and calcium deposits were blue. Helicobacter pylori bacteria were violet to purple. The advantages of the method are its close similarity to H & E staining and technical simplicity. Hemosiderin, H. pylori, mast cell granules, melanin and specific granules of different hematopoietic cells, which are invisible or barely distinguishable by H & E staining, are visualized. Other advantages over previous RG stains include shorter staining time and avoidance of acetone.

Romanowsky-Giemsa as a counterstain for immunohistochemistry: optimizing a traditional reagent.

We describe a detailed protocol for using Romanowsky-Giemsa (RG) counterstaining on formalin fixed, paraffin embedded tissue sections that are stained immunohistochemically (IHC) after antigen retrieval using hot acidic citrate buffer. RG staining is easy to perform and provides consistent results that are similar to hematoxylin and eosin (HE) staining. The counterstaining was applied after a variety of antibodies that used the DAB chromogen and the intensity of IHC stained structures was preserved. Moreover, RG counterstaining provided finer cell detail than HE, methyl green or nuclear fast red. A detailed troubleshooting guide is provided for the RG staining protocol.