Histopathology

Histopathology (or histology) involves the examination of whole tissue samples under the microscope. The pathology lab receives three main types of samples. Samples received by the pathology laboratory require tissue preparation, then are treated and analyzed using techniques appropriate to the tissue type and required research. For immediate diagnosis during a surgical procedure a frozen section is performed Larger specimens include entire organs or parts thereof, which are removed during surgical operations. Examples include a uterus after a hysterectomy, the large intestine after a colectomy, or tonsils after a tonsillectomy. As biopsies, pieces of tissue are removed rather than entire organs, often requiring smaller surgical procedures that can be performed while the patient is still awake but sedated. Biopsies include excisional biopsies, in which tissue is removed with a scalpel (eg, a skin excision for a suspicious mole) or a core biopsy, in which a needle is inserted into a suspicious mass to remove a slip or a tissue center that can be examined. under the microscope (for example, to investigate a lump in the breast). Fluid and very small pieces of tissue (individual cells instead of groups of cells, for example, within the fluid around the lung) can be obtained by fine needle aspiration (FNA). This is done with a thinner needle than that used in a core biopsy, but with a similar technique. This type of material is usually liquid rather than solid and is sent for cytology rather than histology (see Cytopathology).