Anatomic pathology is the branch of pathology that is concerned with the diagnosis of disease based on the gross and microscopic examination of cells and tissues. Contrary to popular belief, the field is mostly concerned with the study of tissue obtained from live patients. In fact, almost all tissues removed from a patient for any reason are examined by a pathologist. The autopsy also remains an important tool in gaining medical knowledge.
Biopsy specimens are often taken when the cause of a disease is uncertain, or its extent or exact character is in doubt. Aditionally, pathologic examination can differentiate between different types of cancer and determine whether a lesion is benign or malignant. Vasculitis is usually diagnosed on biopsy. Larger specimens called resections (similar to an excisional biopsy) are also sent to the anatomic pathologist by the operating surgeon. These specimens generally result from a surgery designed to eradicate a known cancer from a patient, eg. a mastectomy specimen in a patient with breast cancer. Although the diagnosis of breast cancer is made by the pathologist from a breast biopsy, the examination of the mastectomy specimen is important in order to determine the exact nature of the cancer and the extent of it's spread ("staging").
The procedures used in anatomical pathology:
- Gross pathology:
- identification of injuries, retrieval of foreign bodies and surgical material
- examination with the naked eye (this is important especially for large tissue fragments, where diseased parts of an organ can often be visually identified)
- Histopathology and cytopathology:
- examination of stained sections on glass slides with a microscope (most commonly haematoxylin and eosin - a pink and blue stain)
- examination with special stains for iron, organisms, calcium, elastic tissue, mucins etc
- examination with immunoperoxidase and immunofluorescence stains - certain antibodies are especially useful in tumour pathology, in some inflammatory skin diseases and renal biopsies
- Electron microscopy
- Tissue cytogenetics
- Flow immunophenotyping
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