Page 23 - Textbook of Pathology, 6th Edition

diseases such as Alzheimer’s disease, diabetes, cancer, strokes, anatomy, is the classic method of study and still the most 7
etc. There are 2 types of sources of stem cells: embryonic stem useful one which has stood the test of time. The study
cells and adult stem cells. Since embryonic stem cells are more includes structural changes observed by naked eye
numerous, therapeutic cloning of human embryos as a source of examination referred to as gross or macroscopic changes,
stem cells for treating some incurable diseases has been allowed and the changes detected by light and electron microscopy
in some parts of the world. A time may come when by using supported by numerous special staining methods including
embryonic stem cells, insulin-producing cells may be introduced histochemical and immunological techniques to arrive at CHAPTER 1
into the pancreas in a patient of insulin-dependent diabetes the most accurate diagnosis. Modern time anatomic
mellitus, or stem cells may be cultured in the laboratory in lieu pathology includes super-specialities such as cardiac
of a whole organ transplant. Thus, time is not far when organs pathology, pulmonary pathology, neuropathology, renal
for transplant may be ‘harvested’ from the embryo in lieu of a pathology, gynaecologic pathology, breast pathology,
whole organ transplant. dermatopathology, gastrointestinal pathology, oral
In April 2003, Human Genome Project (HGP) consisting of pathology, and so on. Anatomic pathology includes the
a consortium of countries, was completed which coincided with following 3 main subdivisions:
50 years of description of DNA double helix by Watson and 1. Surgical pathology. It deals with the study of tissues
Crick in April 1953. The sequencing of human genome reveals that removed from the living body. It forms the bulk of tissue
human genome contains approximately 3 billion of the base material for the pathologist and includes study of tissue by
pairs, which reside in the 23 pairs of chromosomes within the Introduction to Pathology
nucleus of all human cells. Each chromosome contains an paraffin embedding techniques and by frozen section for rapid
estimated 30,000 genes in the human genome, contrary to the diagnosis.
earlier estimate of about 100,000 genes, which carry the 2. Forensic pathology and autopsy work. This includes
instructions for making proteins. The HGP gave us the ability the study of organs and tissues removed at postmortem
to read nature’s complete genetic blueprint for building each for medicolegal work and for determining the underlying
human being. All this has opened new ways in treating and sequence and cause of death. By this, the pathologist
researching an endless list of diseases that are currently attempts to reconstruct the course of events how they may
incurable. In time to come, medical scientists will be able to have happened in the patient during life which culminated
develop highly effective diagnostic tools, to better understand in his death. Postmortem anatomical diagnosis is helpful
the health needs of people based on their individual genetic to the clinician to enhance his knowledge about the disease
make-ups, and to design new and highly effective treatments and his judgement while forensic autopsy is helpful for
for disease as well as suggest prevention against disease. medicolegal purposes. The significance of a careful
These inventions have set in an era of human molecular postmortem examination can be summed up in the old
biology which is no longer confined to research laboratories but saying ‘the dead teach the living’.
is ready for application as a modern diagnostic and therapeutic 3. Cytopathology. Though a branch of anatomic
tool. Modern day human molecular biology is closely linked to pathology, cytopathology has developed as a distinct
information technology; the best recent example is the subspeciality in recent times. It includes study of cells shed
availability of molecular profiling by cDNA microarrays in which off from the lesions (exfoliative cytology) and fine-needle
by a small silicon chip, expression of thousands of genes can be aspiration cytology (FNAC) of superficial and deep-seated
simultaneously measured.
lesions for diagnosis (Chapter 11).
SUBDIVISIONS OF PATHOLOGY B. HAEMATOLOGY. Haematology deals with the diseases
of blood. It includes laboratory haematology and clinical
After a retrospective into the historical aspects of pathology, haematology; the latter covers the management of patient
and before plunging into the study of diseases in the chapters as well.
that follow, we first introduce ourselves with the branches of
human pathology. C. CHEMICAL PATHOLOGY. Analysis of biochemical
Depending upon the species studied, there are various constituents of blood, urine, semen, CSF and other body
disciplines of pathology such as human pathology, animal fluids is included in this branch of pathology.
pathology, plant pathology, veterinary pathology, poultry D. IMMUNOLOGY. Detection of abnormalities in the
pathology etc. Comparative pathology deals with the study of immune system of the body comprises immunology and
diseases in animals in comparison with those found in man. immunopathology.
Human pathology is the largest branch of pathology. It is
conventionally divided into General Pathology dealing with E. EXPERIMENTAL PATHOLOGY. This is defined as
general principles of disease, and Systemic Pathology that production of disease in the experimental animal and its
includes study of diseases pertaining to the specific organs and study. However, all the findings of experimental work in
body systems. With the advancement of diagnostic tools, the animals may not be applicable to human beings due to
broad principles of which are outlined in the next chapter, the species differences.
speciality of pathology has come to include the following F. GEOGRAPHIC PATHOLOGY. The study of differences
subspecialities:
in distribution of frequency and type of diseases in
A. HISTOPATHOLOGY. Histopathology, used synonymously populations in different parts of the world forms geographic
with anatomic pathology, pathologic anatomy, or morbid pathology.