This document defines pathology and outlines the key steps and tools involved in pathological examination. Pathology is the study of disease through investigation of causes, mechanisms, and tissue changes. The main sources are tissues and organs, and sometimes whole bodies. Examination begins with naked-eye assessment and uses microscopes to analyze tissue samples on a microscopic level, known as histopathology. Specimens can be small biopsies or entire organs. Staining, such as hematoxylin and eosin, helps classify conditions under the microscope. Pathology archives include paraffin blocks, slides, and reports. Autopsies are performed to determine cause and manner of death through external and internal examination of deceased individuals.

1. Nasuhi Engin AYDIN, MD,
Emeritus Professor,
Department of Pathology,
Izmir Katip Çelebi University,
Ataturk Hospital, Izmir
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2. Definition…..
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3. Pathology
Originating from the Greek words
pathos (disease) and logos (knowledge)
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4. Pathology
Is the study disease in respect to; causes (etiology),
mechanisms (pathogenesis) and the changes during
disease processes (pathologic anatomy)
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5. The main source in pathology is tissues
and organs sometimes the whole body !
Pathologic investigation starts with
naked eye examination and finally ends
up with microscopic tissue diagnosis,
i.e.. «histopathology»
The basic instrument is the light
microscope for centuries !!!
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6. Double headed binocular microscope
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7. In this way changes in the tissue structures (morphology)
is assessed both macroscopically and microscopically,
e.g., cancer tissues removed surgically………………………
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8. The scope of pathology………………
Specimens could be small issue fragments
(biopsies) or organ resections or excisions
for evaluation od disease processess
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9. .
With the help of pathological examinations a disease
process can be classified as tumoral or something else !
A total liver specimen

10. Rudolph Virchow
1821 – 1902, the concept of “ cellular pathologyi ”
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11. Prof. Dr. Hamdi Suat Aknar, 1873 - 1936
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Hamdi Suat Aknar has been a milestone in founding
«contemporary pathology» as a student of Virchow

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The first steps in pathologic examination…….
Small tissue fragments
Organ resection…….

13. Automatic tissue processing…..
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Embedding in hard wax (paraffin)

14. Pathology laboratory archives
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Paraffin blocks with tissues

15. Cutting the paraffin embedded tissues as thin as
1/200 mm , i.e., 5 microns
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Microtome is a mechanical instrument

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Tissue sections dried in oven
Stained and coverslipped

17. The most important universal stain (dye) is
the combination of hematoxylin and eosin
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There many histochemical reactions avaliable which forms
the category of special stains in the pathology laboratory,
Mycobacteria stained with Erhlich Ziehl Neelsen (EZN) method
Perls reacion or Prussian blue
reactionfor iron pigments

19. Pathology laboratory archives……….
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20. Pathology laboratory archives……….
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Hard copies or print outs of pathology repotrs

21. Frozen sections for rapid diagnosis during surgery !
Freezing microtome or cryostat

22. Final examination under the microscope, i.e., histopathology

23. For regular routine examinations not requiring
rapid diagnosis tissues are put in chemical solutions
to prevent autolysis, i.e., digestion by their own
proteolytic enzymes.
These chemicals are known as fixatives or fixation
solutions/fluids. Please do not forget that for frozen
sections tissues must be submitted in fresh state
without any solution added.

24. Fixation: Basic rules
1. The most common commercial fixative is formalin
2. A 10% diluted amount is used in at least 10X the
volume of the tissues excised.
3. Second choice is ethyl alcohol avaliable in the clinics

25. While sending tissues for pathologic assessment relevant
clinical information must be submitted !!! And the
pathologist must be able to communicate with the
referring clinician all the time
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26. Autopsy
Originates from the Latin words of auto and opsis,
meaning seeing the self !
Definition: opening (dissecting) the dead body with special
techniques described by various authors, so that a full
examination can be made both externally and
internally to delineate the cause and manner of death.

27. Medical autopsy:
Natural deaths either at hospital or else due to physiological or
pathological causes.
Only can be done by the written consent of the first degree
relatives of the deceased person. Sanitation law article 70 is
an exemption for this which necessitates autopsies to be done in
cases of possible contagious or infectious etiologies for the
benefit of public health
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28. Forensic or legal autopsies :
Deaths due to physical and/or chemical injurious agents,
traumas, accidental, homicidal, suicidal, unexpected sudden
Fatalities are all subjected to forensic or legal investigation.
The legal authorities call for witnesses and medical experts for
this purpose. The consent of the relatives is not sought.
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