1. Special stain 2

2. hemosiderin)) Iron stain
Hemosiderin (storage iron granules) may be present in areas of old hemorrhage or be deposited in tissues with iron overload.
Hemosiderosis is the term used if the iron does not interfere with organ function; but hemochromatosis refers to a condition of iron overload associated with organ failure.

3. Perl's iron stain is the classic method for demonstrating iron in tissues. The section is treated with dilute hydrochloric acid to release ferric ions from binding proteins. These ions then react with potassium ferrocyanide to produce an insoluble blue compound (Prussian blue reaction). Mercurial fixatives seem to do a better job of preserving iron in bone marrow than formalin.

4. Copper - RHODANINE METHOD
Purpose: To identify copper deposits, such as in Wilson's Disease, in the liver.
Principle: It has been suggested that the rhodanine demonstrates the protein to which the copper binds rather than the copper itself.
Results:
Copper deposits: bright red to orange
Nuclei: blue

5. CALCIUM- VON KOSSA'S METHOD
Purpose: Abnormal deposits of calcium may be found in any area of the body. With the H&E stain, calcium appear deep blue-purple.
Principle: Tissue sections are treated with silver nitrate solution, the calcium is reduced by the strong light and replaced with silver deposits, visualized as metallic silver.
Results:
Calcium salts: black
Nuclei: red
Cytoplasm: pink

6. Urate Crystals - Gomori's Methenamine Silver
Purpose: To demonstrate urate crystals.
Principle: The urates take-up the silver, the silver is then reduced to its metallic state.
Results:
Urates: black
Background: green
NOTE: Large calcium deposits may also stain black.

7. Melanin- Fontana-Masson Silver Method
Purpose: To identify argentaffin granules and melanin. Melanin is a non-lipid, non-hematogenous pigment. It is A brown-black pigment present normally in the hair, skin, retina, iris and certain parts of the CNS. Argentaffin granules are found in carcinoid tumors.

8. Principle: A positive argentaffin reaction means the cells take-up silver and then reduce it to a visible metallic state, without the aid of a reducing agent.
Results:
Melanin, argentaffin cells: black
Nuclei: red

9. Fat - Oil Red O
Purpose: To demonstrate fat or lipids in fresh tissue sections. Fat occurring in an abnormal place, such as fatty emboli, and tumors arising from fat cells (liposarcomas) can be differentiated from other types of tumors.
Principle: Staining with oil-soluble dyes is based on the greater solubility of the dye in the lipoid substances than in the usual hydroalcoholic dye solvents.
Results:
Fat: red
Nuclei: blue

10. Fat - Sudan Black
Purpose: For the demonstration of fat (using cryostat sections).
Principle: Sudan Black is slightly basic dye and will combine with acidic groups in compound lipids, thus staining phospholipids also.
Results:
Fat: blue-black
Nuclei: red

11. Collagen - Masson's Trichrome Stain
Purpose: Used to differentiate between collagen and smooth muscle in tumors, and the increase of collagen in diseases such as liver cirrhosis.
Routine stain for liver and kidney biopsies.

12. Principle: As the name implies, three dyes are employed selectively staining muscle, collagen fibers, fibrin, and erythrocytes.
Results:
Nuclei: black
Cytoplasm, muscle, erythrocytes: red
Collagen: blue

13. Chronic active hepatitis
Cerebral abscess
Scleroderma with fibrosis

14. Reticular Fibers - Gordon And Sweet's Method
Purpose: A silver impregnation technique that demonstrates reticular fibers. Reticulum is abundant in liver, spleen, and kidney. Reticulum forms characteristic patterns in relationship to certain tumor cells.
Principle: The tissue is oxidized, then sensitized with the iron alum, which is replaced with silver. The silver is reduced with formalin to its visible metallic state.
Results:
Reticular fibers: black
Nuclei: red

15. Elastic Tissue Fibers - VAN GIESON Technique
Purpose: This stain is useful in demonstrating atrophy of elastic tissue in cases of emphysema, and the thinning and loss of elastic fibers in arteriosclerosis, and other vascular diseases.
With increasing age, changes such as splitting and fragmentation occur, these changes are most obvious in the skin which becomes wrinkled and rather 'loose-fitting'.

16. Principle: The tissue is stained with a regressive hematoxylin, consisting of ferric chloride and iodine.
Results:
Elastic fibers and nuclei: black
Collagen: red
Other tissue elements: yellow