used to stain nuclei blue, while eosin stains the cytoplasm and the extracellular connective tissue matrix of most cells pink. There are hundreds of various other techniques which have been used to selectively stain cells. Other compounds used to color tissue sections include safranin, Oil Red O, congo red, silver salts and artificial dyes. Histochemistry refers to the science of using chemical reactions between laboratory chemicals and components within tissue. A commonly performed histochemical technique is the Perls' Prussian blue reaction, used to demonstrate iron deposits in diseases like Hemochromatosis. Recently, antibodies have been used to stain particular proteins, lipids and carbohydrates. Called immunohistochemistry, this technique has greatly increased the ability to specifically identify categories of cells under a microscope. Other advanced techniques include in situ hybridization to identify specific DNA or RNA molecules. These antibody staining methods often require the use of frozen section histology. These procedures above are also carried out in the laboratory under scrutiny and precision by a trained specialist medical laboratory scientist (a histoscientist). Digital cameras are increasingly used to capture histopathological images. Interpretation The histological slides are examined under a microscope by a pathologist, a medically qualified specialist who has completed a recognised training program. This medical diagnosis is formulated as a pathology report describing the histological findings and the opinion of the pathologist. In the case of cancer, this represents the tissue diagnosis required for most treatment protocols. In the removal of cancer, the pathologist will indicate whether the surgical margin is cleared, or is involved (residual cancer is left behind). This is done using either the bread loafing or CCPDMA method of processing. Microscopic visual artifacts can potentially cause misdiagnosis of samples. Following are examples of general features of suspicious findings that can be appreciated from low to high magnification on histopathology: Architectural patterns Major histopathologic architectural patterns include: Nuclear patterns Major nuclear patterns include: In myocardial infarction After a myocardial infarction (heart attack), no histopathology is seen the first ~30 minutes. The only possible sign the first 4 hours is waviness of fibres at border. Later, however, a coagulation necrosis is initiated, with edema and hemorrhage. After 12 hours, there can be seen karyopyknosis and hypereosinophilia of myocytes with contraction band necrosis in margins, as well as beginning of neutrophil infiltration. At 1 – 3 days there is continued coagulation necrosis with loss of nuclei and striations and an increased infiltration