SURGICAL PATHOLOGY LABORATORY

Surgical Pathology: is the study of lesions of living tissues and cells that are the result of a disease, a trauma , or a malformation

Autopsy : post-mortem examination to discover the cause of death or the extent of disease.

Most of the surgical specimens come from the operating rooms

Others come from emergency rooms or clinics

There are two types of specimens:

organs or parts of organs
biopsies

There are various Histotechnological Techniques

Gross techniques
fixation and fixatives
Tissue processing
Embedding Microtomy
Staining and mounting
Frozen section

Cytology:

Fine needle aspiration biopsy
Exfoliative cytology
Fixation of cytology material
Processing cytology specimen
Staining of cytology material

Gross Examination :

The specimen is properly identified and labeled after its reception in the laboratory.

A properly completed surgical pathology request form contains :

the age and sex of the patient
essential clinical data
type of operation and surgical findings
tissues submitted

Steps to examine material in container

General inspection of specimen with identification of all normal and abnormal parts
Gross description = type of specimen,structures involved, dimensions, weight, shape, color/ lesion, size, color, consistency, relation with adjacent structures

Inadequate gross dissection and sampling will invalidate the microscopic description
A crucial part of pathologic examination is dissection, gross description and selection of sections for microscopic study.
It cannot be remedied if done poorly at the time of the initial workup.
If microscopic description is inadequate, the slide can be reviewed.

Gross examination is crucial because the tissue will be sampled and submitted to histology accordingly.

The specimen is kept wet for 2-3 months

Fixation

Preserves tissues by stopping autolysis

preservation of morphology by inactivation of molecules (ex: enzymes) that change the morphology of a cell
preservation of the chemical integrity

Fixation is accomplished by immersion or perfusion
Mechanism of action: modification of spatial configuration of proteins (denaturing)

Groups of Fixatives

Aldehydes
- Formaldehyde and glutaraldegyde
Mercurials
- B5 and Zenker's
Alcohol: cytology
Oxidizing agents
- dichromate fixative and osmium tetroxide
Picrates
- Buin's Fixatives

Formalin

is a 10% buffered neutral solution

is made up of 40% formaldehyde (100 ml)
distilled water (900ml)
Sodium phosphate, monobasic 4.0 gm
Sodium phosphate, dibasic 6.5 gm
there is 4% formaldehyde in the final liquid
Best general fixative universally used
colorless liquid, or colorless inflammable gas with a sharp odor
Immediate irritant to eyes, nose and throat
Skin and respiratory system particularly affected
Safety precautions include proper ventilation, restricted exposure time and thorough washing if spilled on the skin
Formalin fixes by forming methylene bonds between protein chains

Tissue Processing

There are 3 sequential steps designed to remove extractable water from tissue specimens and replace it with a medium that solidifies to allow sectioning:

Dehydration
Clearing
Infiltration

Processing is done by automatic tissue processor as an overnight schedule that enhances the processing by using heat, vacuum, pressure and agitation

Embedding

is the process of surrounding tissue with a firm substance to facilitate the cutting of the sections

the mostly used embedding medium is parrafin which has a melting point of 56ºC
Stainless steel embedding molds are used for shaping liquid paraffin into blocks
Tissues manually removed from the cassette and put into the molds.
Paraffin should solidify in around 15 minutes: ready for sectioning

Microtomy

The parafin block is inserted in a rotary Microtome

the sections are separated and placed onto a clean pre-marked slide

Staining and mounting

Hematoxylin and eosin (H&E) is a routine stain by which all tissues pass by

The hematoxylin stains nuclei in blue

The Eosin stains cytoplasm in pink or red

It shows the morphology of the tissue

If special biochemical structures are to be stained: special stains for carbohydrates, lipids, amyloid, connective tissue fibers, microorganisms, pigments and minerals

Mounting

Final step in preparation of a slide
Cover the portion containing the tissue with a thin glass: coverslip
This makes the slide permanent and permits microscopic examination
Protects tissue from being scratched and preserves the slide for the years to come.
Mounting media: synthetic resinsFinal step in preparation of a slide

Frozen Section

Sectioning frozen tissue, the tissue being hardened by freezing the water that it contains.
Fresh or fixed tissues are frozen and sectioned instead of being routinely processed and embedded.
Sections done in Cryostat: Microtome in a deep freeze at -20ºC.

Cytology

Cytopathology = study of disease in cells
Exfoliative cytology
Aspiration cytology
Papanicolaou or Pap stain; Main stain for cytologic preparationsCytopathology = study of disease in cells

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