Last updated on November 19, 2018 at 17:16
Pathology, from the Greek words pathos (suffering) and logos (subject), means the «study of suffering». It is both a discipline within medicine and a subject, both of which bridge the basic and clinical sciences.
Pathology deals with the
- Etiology (cause) of the disease
- Morphology (macroscopic, microscopic and submicroscopic description of the disease)
- Pathogenesis (mechanisms of development from the beginning until the manifestation of the disease)
- Clinical significance of the diseases
Pathology as a subject is commonly divided into two parts: general pathology and systemic pathology. General pathology deals with the basic and general processes of diseases, like necrosis, degeneration, inflammation, oncology and immunopathology. Systemic pathology deals with the pathologies of the individual organ systems, like that of the heart, kidney, skin, GIT and so on.
Pathology as a discipline deals mostly with autopsies and biopsies. Autopsy, also called necropsy, is useful in diagnosis of diseases post-mortem, identifying the cause of death, determining different stages of diseases, evaluating the usefulness of a certain therapy and the side effects of therapies.
Biopsy, or surgical pathology, is used for cytology (cell examination) or histology (tissue examination) in living patients. Biopsies can be taken from superficial organs, deep organs or during endoscopy. To take a biopsy from a deep organ (liver, kidney), a method called FNAB, or Fine Needle Aspiration Biopsy is used, where a long needle is led through the skin and into the organ in question. Cells from the organ are then aspirated into a syringe. These cells can then be analyzed by methods like flow cytometry or in situ hybridization.
Biopsies can also be taken by swabbing a certain organ (as opposed to aspiration). This is called an exfoliative biopsy and is done in the case of a Pap smear or swabbing the mouth with a Q-tip for a DNA test.
The gold standard (the best way) to evaluate disease is histopathology, looking at a histological slide of a sample taken from a biopsy, lesion excision or organ resection. This is done by taking the sample and either freezing it or fixing it with formalin and paraffin and stained with HE, called Formalin-Fixed and Paraffin Embedded tissue (FFPE). The freezing method is used when the results are needed ASAP, as it is very fast but doesn’t yield a perfect morphology. It’s often used during operations to determine the borders of tumors for example.
The FFPE method is used in all other cases, as it’s slower, but more accurate and preserves the morphology of the tissue better.
2. Postmortal changes. Cell injury and cell death. Causes of cell injury