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