Embedding Flashcards
Embedding
Enclosing the tissue in infiltration medium, usually paraffin and then allowing the medium to solidify
Embedding Medium
The material used to enclose and support processed tissue, usually paraffin
Cryoconsole
Cold section of the embedding station used to solidify paraffin blocks
Thermoconsole
Used to heat processed tissue and paraffin for embedding
Molds
Contain the molten wax and tissue until fully cooled and solid, gives the block its shape and size
Skin Orientation
Embedded on edge and with all epidermal surfaces facing one side of the mold in the same direction
Tubular Structure Orientation
In cross section so all layers of the tube are visible; lumen, mucosa, submucosa, and muscle
Structures with a Wall Orientation
Ex: cysts or gallbladder On edge (like skin) so all layers are visible
Bone Orientation
At an angle to reduce the surface area in contact with the blade while sectioning
Structures Containing Mucosa Orientation
In cross section so all layers are visible
Aggregate specimen orientation (Like endometrial currettings)
In a line down the center of the block if possible, or clustered together
Effect of overheated embedding medium
Hard, dry, brittle tissue
Optimum temperature of paraffin for embedding
55-58C
Paraffin melting point with respect to thickness, hardness, and ribbons
High melting point gives good thin sections, more support for hard things like bone, and less good for ribbons
lower melting point gives less good thin sections, less support for hard tissues, and ribbons more easily
Importance of preventative maintenance and QC procedures to ensure instrument reliability
Change solutions regularly to prevent contamination
Temperature logs to prevent over hardened tissue
Regular maintenance by a service technician to ensure optimal function
Proper method for embedding a tissue specimen
Open one cassette at a time Fill mold with molten wax add specimen generally orient specimen start cooling complete orientation complete cooling adhere identifying cassette lid leave on cold plate to finish hardening
Two ways orientation can be communicated from grosser to embedder
Mark specimen with ink at the grossing station
Instructions on the side of the cassette
Effects of embedding tissue horizontally
Increases surface area in contact with the blade, can make sectioning more difficult, especially with bone specimens
Effects of embedding on multiple planes
Difficult to get all the relevant tissue in one section
May loose on piece of tissue while trimming to get the other in the same section
Tissue thickness and embedding techniques
Hard to embed tissue that is grossed too thickly, also tends to result in mushy and hard to section tissue
At what stage should embedding orientation be decided?
At the grossing station by the pathologist or PA
What is the most critical step in embedding?
Orientation
What is the best paraffin melting point for routine work?
55-58C
Negative result when: Embedding paraffin is overheated?
over hardened or brittle tissue that is difficult to section, difficult to get ribbons
Negative result when: Soft/lower melting point paraffin is used to embed bone?
Not enough support to get thin, crisp sections
Negative result when: Sections are not embedded flat at the same level?
You can lose a lot of valuable tissue during trimming while trying to get all the pieces in one plane
Or you might lose one piece of tissue while getting to others
Negative result when: A section of bone is not embedded at an angle?
Harder to section because the angle helps reduce the surface in contact with the blade at any given time
Negative result when: The lumen is not visible in a section of fallopian tube?
Unable to visualize all the relevant layers (mucosa, submucosa, muscle) necessary for diagnosis
Negative result when: Forceps are not wiped with gauze between samples?
Carryover of tissue between samples (forceps metastasis), cross contamination of samples
Negative result when: Tissue is cut too thick at the grossing table?
Mush tissue comes out of the processor
might not fit into the cassette or mold
doesn’t section well, might explode on the water bath
Negative result when: The side of the cassette is not read before embedding?
incorrect orientation for type of tissue
may miss the correct number of tissue pieces to be embedded
Negative result when: lens paper containing the tissue is not opened completely?
Might miss small fragments that should have been embedded
Negative result when: Softer paraffin (low melting point) is used to cut kidney at 2 microns?
Too soft to get crisp sections, lots of compression of sections
High melting point paraffin is better for thin sections
Negative result when: Blocks aren’t cooled as rapidly as possible on the embedding center?
Tissue on edge may fall out of alignment
ice crystals may form
Embedding material for Electron Microscopy
Epoxy resins
Embedding material for Nervous System Tissue
Celloidin
Embedding material for Un-decalcified Bone
Glycol Methacrylate (GMA)
Embedding material for Fatty Tissues
Carbowax (water soluble)
Embedding material for Frozen Sections
30% Sucrose
What do you do with floaters in the embedding center?
Put in a blank cassette, label with your initials, the date, and embed the tissue to later identify
What do you do if you chunk a block but there is still tissue left?
Melt down the block and re-embed, especially if you still need more sections from the block
What if a cassette label says 2 pieces, but you only find 1?
Check the embedding center and your immediate surroundings for floaters/jumpers
Check with supervisor
Check trash, etc.
Vas deferens (tubular structure) is embedded longitudinally, rather than in cross-section. What do you do?
Check with the pathologist to confirm whether they wanted longitudinal orientation
Melt down and re-embed in cross-section
Pathologist sees squamous skin calls on a prostate sample, what could have caused this?
Lack of gloves while embedding or picking up slides in the water bath
Wear gloves/ skim water bath regularly/don’t put your fingers in the water-bath
Open cassette to embed a derm, but there’s no sample inside
Check immediate surroundings, trash, supervisor, alert lab
