Histopathology

The study of changes in tissues caused by disease. Histopathology is the examination of biological tissues in order to observe the appearance of diseased cells in microscopic detail.

Histopathology is the examination of tissues from the body under a microscope to spot the signs and characteristics of disease. Histology is the study of tissues, and pathology is the study of disease.

So taken together, histopathology literally means the study of tissues as relates to disease.

A histopathology report describes the tissue that has been sent for examination and the features of what the cancer looks like under the microscope. A histopathology report is sometimes called a biopsy report or a pathology report.

The tissue that is studied comes from a biopsy or surgical procedure whereby a sample of the suspect tissue is selected and sent to the laboratory. It is then processed and cut into very thin layers (called sections), stained and examined under microscopes to characterize the details of the cells in the tissue. For some diseases, the surgeon can get a sample of the tissue interpreted very quickly through the use of frozen sections.

In contrast, cytopathology examines (1) free cells or (2) tissue micro-fragment.

Histopathological examination of tissues starts with surgery, biopsy, or autopsy.

If a large sample is provided e.g. from a surgical procedure then a pathologist looks at the tissue sample and selects the part most likely to yield a useful and accurate.

This part is removed for examination in a process commonly known as grossing or cut up. Larger samples are cut to correctly situate their anatomical structures in the cassette. Certain specimens (especially biopsies) can undergo agar pre-embedding to assure correct tissue orientation in cassette, then in the block & then on the diagnostic microscopy slide. This is then placed into a plastic cassette for most of the rest of the process.

Fine Needle Aspiration Cytology (FNAC) is a simple, quick and inexpensive method, It is a technique whereby cells are obtained from a lesion using a thin needle and smears are obtained for cytopathological diagnosis.

Fine-needle aspiration (FNA) is a diagnostic procedure used to investigate lumps or masses. In this technique, a thin (23–25 gauge), hollow needle is inserted into the mass for sampling of cells that, after being stained, will be examined under a microscope (biopsy).

The sampling and biopsy considered together are called fine-needle aspiration biopsy (FNAB) or fine-needle aspiration cytology(FNAC) (the latter to emphasize that any aspiration biopsy involves cytopathology, not histopathology). Fine-needle aspiration biopsies are very safe minor surgical procedures. Often, a major surgical (excisional or open) biopsy can be avoided by performing a needle aspiration biopsy instead, eliminating the need for hospitalization.

A needle aspiration biopsy is safer and less traumatic than an open surgical biopsy, and significant complications are usually rare, depending on the body site.

This type of sampling is performed for one of two reasons: