Pathology Subdivisions Notes

Subdivisions Of Pathology

Human pathology is conventionally studied under two broad divisions:

General Pathology dealing with general principles of disease and is learnt first; this is followed by learning of Systemic Pathology.

Which includes the study of diseases pertaining to the specific organs and body systems. On the other hand, diagnostic pathology includes

• 1. Morphological and
  2. Non-morphological disciplines as follows.

Read And Learn More: General Pathology Notes

1. Morphological Branches:

These branches essentially involve the application of the microscope as an essential tool for the study and include histopathology, cytopathology, and hematology.

Histopathology:

Histopathology, used synonymously with anatomic pathology,pathologic anatomy, morbid anatomy, or tissue pathology, is the classic method of study and still the most useful one which has stood the test of time for over a hundred years.

• The study includes structural changes observed by naked eye examination referred to as gross or macroscopic changes, and the changes detected by microscopy, which may be further supported by numerous staining techniques such as histochemistry and immunohistochemistry to arrive at the precise diagnosis.
• Modern time histopathology includes sub-specialties such as cardiac pathology, pulmonary pathology, neuropathology, renal pathology, gynaecologic pathology, breast pathology, dermatopathology, gastrointestinal pathology, oral pathology, and so on.

Anatomic pathology includes the following subdivisions:

• Surgical pathology: 
  • It deals with the study of tissues removed from the living body by biopsy or surgical resection.
  • Surgical pathology forms the bulk of tissue material for the pathologist and includes study of formalin-fixed tissue by conventional paraffin embedding technique.
  • Besides, intraoperative frozen sections on fresh unfixed tissue may be employed for rapid diagnosis.
•  Experimental pathology: 
  • This is defined as the production of disease in the experimental animal and study of morphological changes in organs after sacrificing the animal.
  • However, all the findings of experimental work in animals may not be applicable to human beings due to species differences.
• Forensic pathology and autopsy work: 
  • This includes the study of organs and tissues removed at postmortem for medicolegal work and for determining the underlying sequence and cause of death.
  • By this, the pathologist attempts to reconstruct the course of events how they may have happened in the patient during life which culminated in his death.
  • Postmortem anatomical diagnosis is helpful to the clinician to enhance his knowledge about the disease and his judgement while forensic autopsy is helpful for medicolegal purposes.
  • The significance of a careful postmortem examination is appropriately summed up in the old saying ‘The dead teach the living’.

Cytopathology:

• Though a branch of anatomic pathology, cytopathology has developed as a distinct subspecialty.
• It includes a study of cells shed off from the lesions (exfoliative cytology) and interventional cytology by putting a fine-needle and aspirating from superficial and deep-seated lesions for diagnosis (fine-needle aspiration cytology, FNAC).

Hematology:

Hematology deals with the diseases of the blood and blood-forming organs. It includes laboratory hematology and clinical hematology; the latter covers the management of patients as well.

2. Non-Morphological Branches:

These diagnostic branches of pathology include clinical pathology, clinical biochemistry, microbiology, immunology, genetics, and molecular pathology. In these diagnostic branches, qualitative, semi-quantitative, or quantitative determinations are carried out in the laboratory.

The microscope may also be required for some of these lab tests:

• Clinical Pathology:  Analysis of various fluids including blood, urine, semen, CSF, and other body fluids is included in this branch of pathology. Such analysis may be qualitative, semi-quantitative, or quantitative.
• Clinical Biochemistry: Quantitative determination of various biochemical constituents in serum and plasma, and in other body fluids is included in clinical biochemistry. There is likely to be overlapping between clinical pathology and clinical biochemistry.
• Microbiology: This is the study of disease-causing microbes implicated in human diseases. Depending upon the type of microorganisms studied, it has further developed into such as bacteriology, parasitology, mycology, virology, etc.
• Immunology: Detection of abnormalities in the immune system of the body comprises immunology and immunopathology.
• Medical Genetics: This is the branch of human genetics that deals with the relationship between heredity and disease. There have been important developments in the field of medical genetics.
  • For example, In blood groups, inborn errors of metabolism, chromosomal aberrations in congenital malformations and neoplasms, etc.
• Molecular Pathology: The detection and diagnosis of abnormalities at the level of DNA of the cell are included in molecular pathology
  • For example, In situ hybridization, PCR, etc. In sophisticated centers, molecular techniques are now being used as a part of diagnostic pathology reports and for prognostication, besides for research purposes.
• Molecular Cytogenetics: This field of biomedical research and study of diseases combines molecular biology and cytogenetics. This has been possible due to the availability of genome-wide molecular analysis of all aspects of chromosomes to see the biodiversity of an individual’s entire genetic composition
  • For example, In cancers, and chromosomal anomalies. The above divisions of pathology into several subspecialties are quite artificial since overlapping of disciplines is likely, the ultimate aim of pathologists.
  • Being to establish the precise diagnosis, suggest prognosis wherever possible, and understand the causes and mechanisms of disease.
  • Towards this aim, the beginner, as well as the teacher in pathology, remain lifelong learners of pathology, eager to acquire more and more recent knowledge with every passing day.

Subdivisions of Pathology:

The study of Pathology is done under 2 divisions:

1. General Pathology and Systemic Pathology.
2. Diagnostic pathology is practiced as either morphologic branches which invariably require the use of a microscope.
   • For example,  Histopathology, cytopathology, and hematology), or as nonmorphologic branches in which results are generally given as quantitative or semiquantitative values.
   • For example, Clinical pathology, clinical biochemistry, clinical microbiology etc).

Modern Methods In Learning And Practice Of Pathology

Pathology E-Learning:

In the current digital era, learning of pathology is not limited to classrooms and textbooks alone. Several newer online virtual pathology learning platforms are available to eager learners.

• Since pathology is an image-intensive specialty, there are several online repositories of slides as image libraries accompanied by descriptions.
• Then, there are online platforms for self-assessment tests such as objective structured practical and clinical exercises (OSPE and OSCE), e-books with interactive user interfaces, online lectures and courses, etc.
• Inquisitive students are always encouraged to access information from these resources beyond classrooms and textbooks.

Telepathology:

This is defined as the practice of pathology by a remote pathologist utilizing images of tissue specimens transmitted over a telecommunication network.

The main components of a telepathology system are as under:

• Conventional light microscope.
• Method of image capture, commonly a camera mounted on a light microscope.
• Telecommunications link between sender and receiver.
• Workstation at the receiving end with a high-quality monitor.

Depending upon need and budget, telepathology systems are of two types:

• Static (store-and-forward, passive telepathology): In this, selected images are captured, stored, and then transmitted over the internet via e-mail attachment, file transfer protocol, web page, or CD-ROM.
  • It is quite inexpensive and is more common but suffers from the disadvantage of having a sender’s bias in the selection of transmitted images.
• Dynamic (Robotic interactive telepathology): Here, the images are transmitted in real-time from a remote microscope.
  • Robotic movement of a stage of the microscope is controlled remotely and the desired images and fields are accessioned from a remote/local server.
  • Thus, it almost duplicates to perfection the examination of actual slides under the microscope, hence is referred to as Virtual Microscopy.
  • However, image quality and the speed of the internet can be major hurdles.

Digital Slides:

• Digital pathology has reached its zenith with the availability of image digitizing technology for the preparation of virtual pathology slides (VPS) or digital slides.
• By putting the entire glass slide through high-speed scanners and then storing the scanned data in computers having huge memory output (generally in several terabytes).
• By use of high-speed internet, digital slides stored in the memory of one computer can then be accessed, examined, and reported remotely at another location.
• Accessing the VPS data on a computer screen obviates the need for the use of a microscope or serial sectioning.
• Thus, digital slides can be used for tissue diagnosis, storage for records, pathology education, clinical meetings, and quality control.
• However, the moot question remains whether current pathologists used to conventional microscopy will get the same perception on a monitor for diagnostic purposes.

Electronic And Synoptic Pathology Reporting;

With the availability of information systems in modern hospitals and laboratories (HIS and LIS), there is a two-way online information sharing between hospitals and laboratories, thus providing prompt communication and reduced turn-around time.

• Instead of narrative and descriptive reports, modern pathologists provide synoptic or dataset reports, especially in cancers of different organs, which gives uniformity in pathology reporting.
• These pathology report proforma are in the form of templates that have lists of various clinically significant pathologic features of specific lesions/tumors.
• The pathologist just tick-marks positive features in the small boxes in front of each feature and concludes the final report systematically as per the International Classification of Diseases for Oncology (ICD-O).
• These datasets are easily accessible on the websites of the College of American Pathologists (CAP) and the Royal College of Pathologists (RCP).

Must-Know Modern Methods in Learning and Practice of Pathology:

In the current digital era, several alternative resources for e-learning are available for example,  Image libraries, self-assessment platforms having OSPE and OSCE, e-books and lectures, etc.

• Telepathology is the practice of pathology by a remote pathologist via the Internet.
• It may be static in which selected images are sent to another pathologist for opinion or may be robotic (dynamic) in which simultaneous images are seen by the receiving pathologist in real-time.
• Digital (or virtual pathology) slides are scanned glass slides on computer memory.
• Virtual pathology has applications in diagnostic pathology, storage of records, education, clinical meetings, and for quality control.
• Synoptic or dataset reporting in pathology employs a template of important pathologic parameters for various tumors and provides uniformity in reporting.