Fundamental to the diagnosis of bone tumors is the microscopic examination of formalin-fixed, calcified or decalcified tissue embedded in paraffin and stained with hematoxylineosin, interpreted in conjunction with clinical and radiographic data. Hematoxylin-eosin has proved to be one of the most enduring and reliable stains in the entire arsenal of techniques used in diagnostic pathology, including the diagnosis of skeletal conditions.
The majority of bone tumors and tumor like conditions can be accurately diagnosed with the use of this simple staining technique. Hematoxylin stains nuclei blue, and subsequent counterstaining with eosin provides red staining of the cytoplasm and of various extracellular components.
The second component used in the technique (eosin) is an anionic dye that electrostatically binds various proteins. The hematoxylin-eosin stain enables accurate microscopic evaluation of a tissue’s architecture and cells.
This technique is certainly not perfect and occasionally must be supplemented with so-called special techniques.
Special techniques are used when specific diagnostic, pathogenetic, or etiologic questions cannot be satisfactorily answered with the use of the standard approach. This chapter briefly discusses some of the techniques that have potential applications in the diagnosis of bone tumors.
Periodic acid-Schiff StainThe principle of periodic acid-Schiff (PAS) stain is based on the oxidizing reaction in the presence of periodic acid and Schiff’s reagent. Molecules containing vicinal glycol groups form in presence of periodic acid dialdehydes that combine with Schiff’s reagent to produce a reddish (magenta) substance.
Periodic acid-Schiff stain is principally used to demonstrate intracytoplasmic glycogen. The stain by itself is nonspecific but with diastase diagestion (reduction or elimination of a substance positive for periodic acid-Schiff after enzymatic treatment) demonstrates the presence of glycogen.
In bone tumors, it is most often used to demonstrate glycogen in Ewing’s sarcoma and clear-cell chondrosarcoma. In general, periodic acid-Schiff stain can be used to demonstrate the presence of neutral mucin to outline the basement membrane and to visualize fungal and parasitic organisms.
Mucins
Stains for mucins are frequently used in the diagnosis of adenocarcinoma. In bone, they are occasionally used in the diagnosis of metastatic adenocarcinoma when the tumor cells do not form conspicuous glandular structures. Alcian blue combined with Periodic acid-Schiff stains is used to demonstrate neutral and slightly acidic types of mucosubstances.
Meyer’s muciarmine is probably the stain used most frequently to demonstrate acidic mucin. These stains are useful in demonstrating both in tracellular and extracellular mucins in chordoma.
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