Transcript lecture1-INTRODUCTION TO PATHOLOGY by Sufia Husain 2013.ppt

INTRODUCTION TO
PATHOLOGY
SUFIA HUSAIN
ASSIT. PROF & CONSULTANT
PATHOLOGY
KKUH, RIYADH
DEFINITION OF PATHOLOGY
Pathology is the study of disease by scientific
methods. It is the study of changes which occur in
cells and tissues as a result of any injury to the
cell or tissue.
 It originates from 2 Latin words “patho” & “logy”.
‘Patho’ means disease and ‘logy’ means study.
 Diseases is defined as an abnormality in
structure or function of any part of the body.
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The following are the four major aspects studied
as part of pathology of any disease.
1. Etiology,
2. Pathogenesis,
3. Morphologic changes and
4. Functional alteration and clinical features (signs and
symptoms)
1. ETIOLOGY
Etiology of a disease means the cause of the disease.
Knowledge of the primary cause is important in order
to diagnosis understood, & treat any disease.
 If the cause of the disease is unknown it is called
idiopathic/ cryptogenic/ essential etc.
There are two major classes of etiologic factors:
 Genetic e.g. Down’s syndrome(extra chromosome 21),
it is a chromosomal abnormality
 Acquired
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Infectious: bacterial, viral, fungal.
Nutritional: e.g. protein energy malnutrition
Chemical: e.g. alcohol cause liver disease
Radiation: e.g. thyroid cancer after radiation to neck. Post
radiation skin cancer etc.
Mechanical: e.g. road traffic accident
2. PATHOGENESIS
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Pathogenesis is the mechanism through which the
cause leads to the pathological and clinical
manifestations.
The pathogenetic mechanisms could take place in the
latent or incubation period.
Pathogenesis leads to morphologic changes.
The four basic pathogenetic mechanisms are as
follows:
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Inflammation
Degenerative
Carcinogenesis
Immunological
All these will be dealt with in later chapters
3. MORPHOLOGIC CHANGES
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The morphologic changes are the structural changes
that take place in cells or tissues after any pathogenic
mechanisms.
These morphological changes can be seen grossly with
the naked eye or sometimes they can only be seen
under the light microscope.
Changes that are seen with the naked eye are called
gross morphologic changes & those that are seen
under the microscope are called microscopic changes.
In many cases a particular gross or microscopic
change is seen only in a particular disease, i.e. they
may be specific to that disease. And such morphologic
features are used by the pathologist to diagnose the
disease.
4. FUNCTIONAL ALTERATIONS AND CLINICAL
FEATURES
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The altered morphology will affect the normal
function of the affected organ and this will lead to
the development clinical features (signs &
symptoms) of a disease.
Symptoms: is something experienced and reported by
the patient e.g. ‘I am feeling tired’, ‘I have a
headache’ etc.
 Signs: are findings discovered by the physician
during examination of the patient e.g. doctor finds a
lymph node when he/she examines the neck of
patient or doctor find a liver or spleen enlargement
while palpating the abdomen etc.
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PATHOLOGY
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Etiology
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Pathogenesis
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Morphological or chemical alteration
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Clinical features (signs and symptoms)
EPIDEMIOLOGY
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Epidemiology:
Study of the occurrence and distribution of health-related
diseases or events in specified populations, including the
study of the determinants influencing such states, and the
application of this knowledge to control the health problem
(Porta M, Last J, Greenland S. A Dictionary of
Epidemiology, 2008).
It is the study of the patterns, causes, and effects of health
and disease conditions in defined populations.
EPIDEMIOLOGY
 Epidemiology studies the various data and statistics of
diseases to provide information regarding the following
titles in any disease in a particular population or race:
1.
2.
3.
4.
5.
Sex: certain disease are more common in men and certain in
women
Age: various conditions are seen in various age groups
Race: some race are more predisposed to certain disease
Occupation: e.g. people working in asbestos industry can
have asbetosis or mesotheliomas. People working in aniline
dye industry can have urinary bladder cancer etc.
Geographic location: e.g. Under-developed countries has
more malnutrition and infection like tuberculosis. Developed
countries have more cardiac problems, obesity related
diseases etc.
EPIDEMIOLOGY
Socioeconomic strata: also affects the type of disease
Prevalence: is the total number of cases of a particular
disease in a particular defined population in a particular
period of time.
8.
Incidence: is the number of new cases of a particular
disease in a defined population in a defined period of
time. It measures the rate of occurrence of new cases.
9.
Sequalea: it is the complication or the consequence of a
disease.
10. Prognosis: it is the expected outcome of the disease. It is
the clinician’s estimate of the severity and possible
results of the disease.
11. Morbidity: is the presence and extent of illness
12. Mortality rate is a measure of the number of deaths (in
general, or due to a specific cause) in a defined
population, during a defined period of time. It is
expressed in units of deaths per 1000 individuals per
year.
6.
7.
PURPOSES AND IMPORTANCE OF EPIDEMIOLOGY
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To investigate the extent of a disease in a community.
To study natural history and prognosis of disease
To identify causes and risk factors
To provide good health care based on the findings.
To recommend and assist in various interventions done to
prevent or treat disease (preventive and therapeutic
measures), e.g. immunizations, to develop screening
programs for different disease etc.
To evaluate all health care facilities and programs.
It is the cornerstone of public health, and informs policy
decisions. To provide foundation for public policy.
THEREFORE IN MEDICINE DISEASE IS STUDIED
UNDER THE FOLLOWING HEADINGS:
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Definition
Epidemiology of disease
Clinical features/presentation: signs and symptoms
Pathogenesis
Morphology: it is divided into
 Gross/ macroscopic- visible to the naked eye
 Microscopic- visble under a microscope
Differential diagnosis: is there any other alternative
diagnosis/diagnoses
Treatment and management
Prognosis
CLASSIFICATION OF DISEASE BASED ON ETIOLOGY AND
PATHOGENESIS
I. CONGENITAL DISEASE: is a condition existing
at birth and often before birth, or that develops
during the first month of life, regardless of
causation. They can be:
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Genetic/ chromosomal: e.g. hemophilia which is an
x-chromosome linked disorder), Down syndrome,
inborn error of metabolism etc
Non-genetic: e.g. a birth defect like cleft lip/palate
or spina bifida.
CLASSIFICATION OF DISEASE BASED ON ETIOLOGY AND
PATHOGENESIS
II. ACQUIRED DISEASES: They can be:
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Inflammatory e.g. rhematoid arthiritis, dermatitis
Infective e.g. bacterial, viral, fungal
Vascular or Immune mediated e.g. atherosclerosis (causes stroke and
heart attack), vasculitis etc.
Degenerative e.g. Alzheimer’s disease
Neoplastic (growth disorder) e.g. cancer
Drug related e.g. liver or kidney failure secondary to certain drugs
Metabolic e.g. gout, diabetes mellitus etc.
Nutritional deficiency diseases may arise as a result of poor supply,
interference with absorption, inefficient transport within the body, or
defective utilization. It may take the form of deficiency either of major
classes of food, usually protein and energy, or vitamins or elements
essential for specific metabolic processes, e.g. iron for haemoglobin
production.
COURSE OF DISEASE
The course of a disease in the absence of any intervention is called the
natural history of the disease. The different stages in the natural history
of disease especially infectious include:
a) Exposure to various risk factors (causative agents)
b) Latent period between exposure and onset of disease. Incubation
(induction) period refers to variable period of time without any obvious
signs or symptoms from the time of exposure
c) Onset of disease: the disease may remain asymptomatic or subclinical
(i.e. without any clinical manifestations), or may lead to overt clinical
disease.
d) Outcome and consequences of disease: Following clinical onset, disease
may follow any of the following trends:
 resolution or recovery with or without complication or sequalae can
occur or,
 The disease can settle down, but sequelae are left or,
 Natural recovery i.e. recovery without any intervention, can occur at
any stage in the progression disease or,
 It may result in death.
SIGNIFICANCE OF PATHOLOGY
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Understanding pathology will help to understand how
the clinical features of different diseases occur & how
to treat them.
It will teach the health care workers how to handle &
help their patients in a better & scientific way.
It is for these reasons that it is essential to study
pathology.
In addition, the pathologist can use the morphologic
changes seen in diseases to diagnose different
diseases.
There are different diagnostic modalities/instruments
used in pathology. Some of the instruments used in
pathology are light microscope, immunofluorescent
microscope electron microscope.
LIGHT MICROSCOPY
IMMUNOFLUORESCENCE
MICROSCOPY
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Immunofluorescence is a
common technique using a
fluorescence microscope With
special blue filter. This
technique uses antibodies
chemically linked to a
fluorescent dye to identify or
quantify various antigens in a
tissue sample.
This method of study focuses
on the immune response that
occurs within a diseased tissue
or its cells.
It helps in diagnosing various
diseases.
ELECTRON MICROSCOPE
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The electron microscope is
a type of microscope that
uses electrons to create an
image of the target.
It has more magnification
power than a normal light
microscope. Modern
electron microscopes can
magnify objects up to two
million times.
It enables us to see cell
structure like
mitochondria, endoplasmic
reticulum, viral particles
etc. It is also called as
ultra structural studies.
This is a
hydrothermal worm.
It is so tiny it
requires a electron
microscope to see it.
The organism, only
slightly larger than
a bacterium, lives in
deep sea near or
beneath the Earth's
hot crust (This striking
image, captured by Phillippe
Crassous taken using
scanning electron microscope).
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A tardigrade, or "water bear"
is seen through an electron
microscope.
Less than 1 mm in length,
they can withstand harsh
environmments and still
thrive. They're known as
"extremophiles" .
These life forms thrive under
the most extreme conditions
e.g. under thousand-years-old
layers of ice, extreme heat,
volacano. They withstand
radiation bombardment and
still reproduce. They bathe in
acid and keep on going. The
can be dried, dehydrated and
desiccated, yet still go about
their business. (And you
thought your days were
challenging!)
Extremophiles, are life forms
that inhabit what human
beings consider "hostile"
environments.
DIAGNOSTIC TECHNIQUES USED IN PATHOLOGY OR
THE VARIOUS SUBDIVISIONS IN PATHOLOGY
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Histopathology
Cytopathology
Immunohistochemistry
Hematopathology
Chemical pathology/ clinical biochemistry
Microbiology
Immunology
Toxicology
Cytogenetics
Molecular techniques
Autopsy
1) HISTOPATHYOLOGY
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Histopathology studies tissues under the microscope.
Tissues for histopathological examination are obtained by
biopsy. Biopsy is a tissue sample from a living person to
identify the disease. Biopsy can be either incisional or
excisional.
Once the tissue is removed from the patient, it has to be
immediately fixed by putting it into adequate amount of
10% Formaldehyde (10% formalin) before sending it to
the pathologist. The purpose of fixation is to prevent
autolysis and bacterial decomposition and putrefaction.
When the tissue reaches the lab the pathologist examines
it macroscopically (i.e. naked-eye examination of tissues).
They then either put the entire tissue for processing or
choose parts of tissue for processing depending on the
requirment.
1) HISTOPATHYOLOGY CONTD…
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The tissue is processed is special way resulting in very thin
tissue slices (i.e. 4 to 6 microns) and the slices are then placed
on a slide with the help of an adhesive. The end result is thin
slices of tissue on a slide tissue ready for staining with various
kinds of stains ( e.g. H&E stain or other special stains such as
PAS, Immunohistochemistry, etc...)
The Hematoxylin/Eosin (H&E) stain is routinely used to stain
the selected tissue part. It gives the nucleus a blue color & the
cytoplasm & the extracellular matrix a pinkish color. Then the
pathologist will look at the tissue structures under the
microscope. And based on this abnormal morphology he/she
will make the diagnosis.
Histopathology is usually the gold standard for pathologic
diagnosis.
HISTOPATHOLOGY SLIDES READY TO BE EXAMINED
UNDER A LIGHT MICROSCOPE
2) CYTOPATHOLOGY
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Cytopathology is the study of cells from various body sites to
determine the cause or nature of disease. It is used for the
purpose of:
 Screening for cancer e.g. cervical cytology is used in the
screening of carcinoma of cervix.
 Diagnosis of disease especially cancer
The advantage of cytologic technique when compared to
histopathological techniques is that the procedure is cheap, takes
less time and requires no anesthesia.
a)
b)
a
b
Histology
Cytology
2) CYTOPATHOLOGIC
METHODS
There are different cytopathologic methods including:
a)
Fine-needle aspiration cytology (FNAC): It is the suction of
cells from diseased organ. In FNAC, cells are obtained by
aspirating the diseased organ or a suspicious mass using a thin
bore needle under negative pressure. The cells thus obtained are
stained and examined under a microscope. Most of the organs
can be sampled by fine-needle aspiration.
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When the mass lesion is superficial and grossly papable then
the FNA is done directly e.g. organs like thyroid, breast,
lymph nodes, skin and soft tissues.
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In deep seated organs e.g. lung, mediastinum, liver etc. the
mass lesion is detected with the help of radiology, then an
ultrasound guided or CT Scan guided FNA is performed.
2) CYTOPATHOLOGIC METHODS CONTD…
b) Exfoliative cytology: In this case the cells are
scraped of the mucosa using a spatula (e.g. cervix and
oral cavity) or the cells exfoliate themselves and
collect in a particular type of secretion (e.g. the cells
lining the bronchus of the respiratory tract that
collect in the sputum or in case of a urinary tract
disease the cells which exfoliate collect in the urine).
The material obtained is smeared (spread) on a glass
slide, fixed and stained and then studied under a
light microscope. Examples of exfoliative cytology
include sputum, cerebrospinal fluid, urine, effusions
in body cavities (pleura, pericardium, peritoneum),
nipple discharge and vaginal discharge.
PAP SMEAR (STEPS 1,2,3 AND 4
(1)
(3)
(4)
(2)
3. Hematology
 It is a study of abnormalities of the cells of the
blood and their precursors in the bone marrow. It
is used in the diagnosis various types of anemia
& leukemia.
4. Immunohistochemistry
 This is a specialized staining procedure is used to
detect a specific antigen in the tissue in order to
identify the type of disease.
5. Biochemical examination
It is the analysis of bodily fluids and biochemical tests are used for
diagnosis and management. It is used to detect and quantitate various
normal and abnormal compounds in the blood, urine, etc.
6. Microbiology
It is the study and diagnosis of organisms responsible for various infectious
diseases
7. Immunology
It is the analysis of the immune system of the body.
8. Toxicology
It is the study and identification of various poisons and toxic substances.
9. Cytogenetics (clinical genetics)
it is a study of chromosomal abnormalities.
10. Molecular techniques
various molecular techniques such as fluorescent in situ hybridization,
Southern blot are used to detect genetic diseases.
11. AUTOPSY
It is a sub-specialty that focuses on determining
the cause of death by examining a dead body. The
autopsy informs about the pathologic process, the
injury, or the disease that directly results in or
initiates a series of events that lead to a person's
death. It can be homicidal, suicidal, accidental,
some active pathologic disease (like cancer ,
cardiovascular disease) natural etc.
 The pathologist can perform the autopsy. It also
provides useful information about various
disease. It can be used in research. Also it can be
used as a tool to educate students, surgeons etc
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ROLE OF DIAGNOSITIC PATHOLOGY
IN DISEASE MANAGMENT
Any patient presenting to a clinic is generally
subjected to history taking, clinical, radiological
and pathological examination in order to come to
a diagnosis. Among the pathological
examinations the are almost always asked to do
various blood and urine tests. Sometimes they
are asked to undergo a cytological or
histopathological test (or any of the other
pathological techniques mentioned before) in
order to obtain an accurate diagnosis.
 This way pathology plays an essential role in the
management of the patient and diagnosis of their
disease and therefore their treatment.
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