Histopathology is the microscopic examination of biological tissues to observe the appearance of diseased cells and tissues in very fine detail.
The word 'histopathology' is derived from a combination of three Greek words:
- histos meaning tissue,
- pathos meaning disease or suffering, and
- logos which refers to study in this context*.
Hence histopathology is the study of microscopic changes or abnormalities in tissues that are caused as a result of diseases.
Uses of Histopathology
The main use of histopathology is in clinical medicine where it typically involves the examination of a biopsy (i.e. a surgically removed sample or specimen taken from a patient for the purposes of detailed study) by a specialist physician called a pathologist. Depending on his or her specialist training and main area of work, the pathologist may be more accurately referred to as a histopathologist because medical specialists who study and interpret diseased tissues in microscopic detail are histopathologists. However, in the cases of some pathologists, examination of diseased tissues in microscopic detail may only be a relatively minor part of their overall professional responsibilities so the term 'histopathologist' may not always be used. A pathologist or histopathologist studies specimens of cells and tissue after a sample has been removed from the patient, processed using special histological techniques - some of which are summarised on the page about how to prepare histology slides, and carefully prepared histological sections of the specimen have been placed on slides and stained using histology stains ready for observation using a microscope. Either a light microscope or an electron microscope may be used to examine histology slides.
Histopathologists are medical specialists who have broad knowledge and understanding of the pathological and clinical aspects of disease. They work with a wide range of patients and medical conditions as well as with many other medical professionals who have expertise in associated disciplines, as well as with an ever-increasing range and complexity of technologies including some medical imaging equipment such as electron microscopes. Sub-specialties associated with histopathology include cytopathology, forensic pathology, neuropathology and paediatric pathology.
Although clinical medicine (which is a term that refers to the context of diagnosing, treating, or trying to treat and advise a patient) is a very important application of histopathology, histopathology is not only used in clinical medicine.
Diseased cells and biological tissues are also studied in microscopic detail for other reasons, such as to:
- investigate crimes e.g. look for causes of injury or death such as evidence of tissue damage by poisons, drugs or possibly deliberately targeted biological pathogens - Forensic Pathology or Forensic Histopathology.
- investigate historical artefacts containing biological tissue in sufficiently good condition to learn about the health of long-deceased individuals - which can involve various types of histology and histopathology, e.g. bone histology, dental histology and so on. This is similar to the
- study of ancient diseases (an area of study known as 'paleopathology', sometimes spelt 'palaeopathology') using histological techniques - Histology in Palaeopathology, or Histopalaeopathology.
What is the difference between Histology and Histopathology ?
- Histology is the microscopic examination and study of biological cells and tissues (using certain techniques).
- Histopathogy is the microscopic examination and study of diseased biological cells and tissues (using the same set of techniques that may be generally referred to as 'histological techniques').
So, producing and studying histology slides of healthy tissues, e.g. for educational purposes, may be described as 'histology' but not as 'histopathology'. Conversely, producing and studying histology slides of diseased tissues, e.g. for clinical diagnosis, may be called 'histology' but is more accurately described as 'histopathology'.
Histology and Histopathology are often discussed and described together, e.g. "The Histology and Histopathology of [specific tissue type or part of the body]". This makes sense because it is often necessary to prepare histology slides of a sample or specimen and examine them first in order to find out if the cells or tissue are, or are not, diseased. That is more likely to be true in cases of histology for medical education / training and for historical research than in clinical situations where there may also be various other indications of the presence disease, or specific diseases, to take into consideration.