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histopathology lecture > Faults > Flashcards

Faults Flashcards

1
Q

Faults: Sections expand or disintegrate on water bath
Reason:

A

Poor impregnation of tissue
Water temperature too high in flotation bath

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2
Q

Faults: Sections expand or disintegrate on water bath
Remedy:

A

Re-process tissue
Turn down the temperature of the flotation bath

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3
Q

Faults: Sections roll into a coil instead of remaining flat on knife edge
Reason:

A

Blade dull
Rake angle too small
Section too thick

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4
Q

Faults: Sections roll into a coil instead of remaining flat on knife edge
Remedy:

A

Use a new blade
Reduce blade tilt if clearance angle is excessive
Reduce section thickness

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5
Q

Faults: Grooved, Scored, smeared and deformed sections
Reason:

A

Dull knife /blade edge
Too warm room

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6
Q

Reason:
Dull knife /blade edge
Too warm room

A

Remedy:
Re-sharpen the knife/blade or move the existing blade to an unused surface or replace it with a new one

Cool/change the temperature of the room or cool the block in ice water

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7
Q

Faults: Sections fail to form ribbons
Reasons:

A

Surfaces and edges of the block are not parallel
Horizontal surface of the block is not parallel to the knife
Paraffin wax is too hard
Knife is tilted too much
Sections are too thick
Knife is dull

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8
Q

Remedy: Re-trim the block
Re-adjust and re-orient the block
Coat horizontal edges of the block with wax of lower melting point
Reduce the tilt
Re-adjust thickness of the section
Hone and strop

Reason:

A

Surfaces and edges of the block are not parallel
Horizontal surface of the block is not parallel to the knife
Paraffin wax is too hard
Knife is tilted too much
Sections are too thick
Knife is dull

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9
Q

Fault: Sections roll up on cutting so that they adhere and get broken against the knife edge

Reason:

A

Knife is blunt
Tilt of knife is too great
Knife edge is dirty

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10
Q

Reason: Knife is blunt
Tilt of knife is too great
Knife edge is dirty

Remedy:

A

Sharpen the knife
Reduce the tilt
Clean the knife edge

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11
Q

Faults: Ribbon is curved, crooked or uneven instead of straight

Reason:

A

Blunt of dull spot on the knife, producing an irregular knife edge
Edges of the block are not parallel but round or wedge shape
Knife is not parallel to the block
Paraffin is impure

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12
Q

Reason: Blunt of dull spot on the knife, producing an irregular knife edge
Edges of the block are not parallel but round or wedge shape
Knife is not parallel to the block
Paraffin is impure

Remedy

A

Adjust the knife so that knife edge will present a uniformly sharp edge to the block or sharpen

Re-trim the block

Readjust knife and block

Repeat impregnation using pure wax

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13
Q

Faults: Sections are compressed wrinkled or jammed
Reason:

A

knife is blunt or dull
Paraffin block is warm and soft
Knife edge is coated with paraffin
Sections are too thin
Microtome set screw is loose
Tilt of knife is too vertical
Too rapid cutting
Too warm room
Unparallel block edges

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14
Q

Reason:
Knife is blunt or dull
Paraffin block is warm and soft
Knife edge is coated with paraffin
Sections are too thin
Microtome set screw is loose
Tilt of knife is too vertical
Too rapid cutting
Too warm room
Unparallel block edges

Remedy

A

Re-sharpen the knife
Cool the block on ice water until firm
Clean the knife edge
Re-adjust thickness of section
Tighten screw
Reduce the tilt
Decrease cutting speed for every thin section
Cool/change the room temperature or cool the block in ice water
Trim the block edges until they are parallel

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15
Q

Faults: Sections are squashed (width of each section is less than that of block)
Reason:

A

Bevel of knife is lost due to incorrect sharpening

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16
Q

Reason: Bevel of knife is lost due to incorrect sharpening

Remedy:

A

Re-sharpen using a knife back or automatic knife sharpener

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17
Q

Fault: A hole is formed in the section
Reason:

A

Bubble or dirt formed in the embedding medium
Hard spot in tissue due to calcium
Excessive dehydration or improperly processed tissue

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18
Q

Reason:

Bubble or dirt formed in the embedding medium
Hard spot in tissue due to calcium
Excessive dehydration or improperly processed tissue

Remedy:

A

Re-embed in freshly filtered wax if necessary

Once embedded in paraffin wax, decalcification is impractical; use a base sledge microtome with a wedge knife

Expose the tissue, then soak the block in ice water or with a piece of cotton before sectioning

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19
Q

Faults: Sections of unequal thickness are
produced

Reasons:

A

Tilt of knife is too great or bevel is not cleared hence object is compressed against the knife edge

Clamp set screw on knife or blockholder is loose

Blocks are too large

Blocks are too hard

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20
Q

Reasons:
Tilt of knife is too great or bevel is not cleared hence object is compressed against the knife edge

Clamp set screw on knife or blockholder is loose

Blocks are too large

Blocks are too hard

Remedy:

A

Reduce the tilt

Tighten the screw

Cut blocks into smaller fragments

Soften the blocks in detergent or phenol

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21
Q

Faults: Sections adhere to the knife or other parts of the microtome

Reason:

A

Static electricity due to low atmospheric humidity
Knife edge is dirty
Knife edge is dull
Tilt of knife is too great

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22
Q

Reason:

Static electricity due to low atmospheric humidity
Knife edge is dirty
Knife edge is dull
Tilt of knife is too great

Remedy:

A

Breathe out or blow gently on the block and knife to breakup static electricity , or boil water in the room to increase humidity

Clean knife edge

Sharpen the knife ü Reduce tilt

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23
Q

Fault: Ribbon is split or lengthwise vertical scratches are seen on sections

Reason:

A

Nicks or damage on the knife edge
Dirty embedding
Knife edge is dirty
Tilt of knife is too great

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24
Q

Reason:
Nicks or damage on the knife edge
Dirty embedding
Knife edge is dirty
Tilt of knife is too great

A

Sharpen the knife
Re-embed in filtered wax
Clean knife edge with xylene
Reduce the tilt

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25
Q

Fault: Sections are lifted from the knife on the upstrokes

Reason:

A

Knife tilt is too great
Knife is dull
Paraffin is too soft or room temperature is warm

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26
Q

Reason:

Knife tilt is too great
Knife is dull
Paraffin is too soft or room temperature is warm

Remedy:

A

Reduce the tilt
Sharpen the knife
Cool paraffin wax in ice water

27
Q

Fault: Resistance is felt on the lower part of the section during cutting

Reason:

A

Tilt of knife is too small, paraffin block is therefore compressed against the base of the knife towards the end of stroke

28
Q

Reason:
Tilt of knife is too small, paraffin block is therefore compressed against the base of the knife towards the end of stroke
Remedy:

A

Increase the tilt

29
Q

Fault: Horizontal or parallel lines or furrows across the section (chatters) are seen, forming thin and thick zones

Reason:

A

Knife edge vibrates due to hardness of tissue
Tilt of knife is too great
Overhydration or lack of moisture in tissue
Use of dull knife/blade
Cutting too quickly

30
Q

Reason:
Knife edge vibrates due to hardness of tissue
Tilt of knife is too great
Overhydration or lack of moisture in tissue
Use of dull knife/blade
Cutting too quickly

Remedy:

A

Treat with phenol during processing or collodionize
Reduce tilt
Restore moisture of tissue by letting the block stand and soaking it briefly in ice water or by placing it face down on an ice tray
Resharpen the knife/blade
Decrease cutting speed

31
Q

Section cut is sometimes thin sometimes thick
Reason:

A

Knife is blunt
Knife is not clamped properly
Tilt of knife is too great
Knife or block holder is loose
Knife tilt is too small that block is compressed by bevel and section is not cut

32
Q

Knife is blunt

Knife is not clamped properly

Tilt of knife is too great

Knife or block holder is loose

Knife tilt is too small that block is compressed by bevel and section is not cut

Remedy:

A

Sharpen the knife
Adjust the knife
Reduce tilt
Tighten adjusting and locking screw
Increase the tilt

33
Q

Faults: Knife makes a hard metallic scrapping or ringing sound on backstroke, when section is cut

Reasons:

A

Tilt of knife is too slanted or too big
Tissue is too hard
Knife blade is too thin

34
Q

Remedy for
Tilt of knife is too slanted or too big
Tissue is too hard
Knife blade is too thin

A

Readjust the angulation of the knife

Take fresh block treated with phenol during processing

Change the knife

35
Q

Faults:
Frozen tissue crumbles and comes off the block holder when cut

Reason:

A

Freezing is not adequate

36
Q

Reason: Freezing is not adequate
Remedy:

A

Refreeze the tissue block

37
Q

Faults: Frozen tissue chips into fragments when cut
Reason:

A

Tissue is frozen too hard

38
Q

Tissue is frozen too hard
Remedy:

A

Warm the tissue with the fingers

39
Q

Faults: Pleated, folded and crooked ribbons
Reason:

A

Imperfections in the blade edge, i.e. the horizontal edges are not parallel or the lower block edge is not parallel to the knife edge when sectioning

40
Q

Imperfections in the blade edge, i.e. the horizontal edges are not parallel or the lower block edge is not parallel to the knife edge when sectioning

Remedy:

A

Trim the block parallel to the other edge or re-embed them in molds so that the edge of blocks is parallel to the knife edge

Try another part of the knife edge

41
Q

Fault: Brittle or Hard tissues
REASON:

A

Prolonged fixation
Prolonged dehydration
Prolonged clearing
Prolonged paraffin infiltration
Overheated paraffin oven
Drying out of tissue before actual fixation

42
Q

Prolonged fixation
Prolonged dehydration
Prolonged clearing
Prolonged paraffin infiltration
Overheated paraffin oven
Drying out of tissue before actual fixation

Remedy

A

Tissue may be softened by soaking in a small dish or bowl containing water with detergent, phenol or molliflex

43
Q

Clearing agent turns milky as soon as tissue is placed in it

Reason

A

Water not completely removed du to
incomplete dehydration

44
Q

Water not completely removed du to
incomplete dehydration

Remedy

A

Repeat dehydration with absolute alcohol then clear
again

45
Q

On trimming, tissue smells of clearing agent

Reason

A

Clearing agent not completely removed due to insufficient impregnation

46
Q

Clearing agent not completely removed due to insufficient impregnation

Remedy

A

Block is trimmed down nearest to the tissue. Remaining wax is melted on embedding oven and
paraffin impregnation is repeated, changing the paraffin at least once before blocking

47
Q

Tissue is opaque, section cutting is difficult due to presence of alcohol

Reason:

A

Insufficient clearing

48
Q

Insufficient clearing

A

Repeat clearing; if object has already been embedded, prolong clearing up to 12 hours, then re-embed

49
Q

Tissue shrinks away from wax when trimmed
Reason:

A

Insufficient dehydration therefore incomplete clearing and impregnation

50
Q

Insufficient dehydration therefore incomplete clearing and impregnation
Remedy:

A

Repeat the whole procedure

51
Q

Tissue is soft when block is trimmed
Reason:

A

Incomplete fixation

52
Q

Incomplete fixation
Remedy:

A

Repeat whole procedure

53
Q

Fault: Airholes are found on tissue during trimming
Reason:

A

Incomplete impregnation

54
Q

Incomplete impregnation

Remedy

A

Repeat impregnation

55
Q

On trimming wax appears crystalline

Reason:

A

Contaminated wax
Block not cooled rapidly enough

56
Q

Reason: Contaminated wax
Block not cooled rapidly enough

A

Re-embed in freshly filtered wax

57
Q

Paraffin block, after cooling is moist and crumbles

Reason:

A

Insufficient paraffin impregnation

58
Q

Insufficient paraffin impregnation

Remedy

A

Repeat paraffin impregnation, then re-embed

59
Q

Inadequate processing of fatty tissues

reason:

A

Routine schedule and reagents may not process fat adequately

60
Q

Routine schedule and reagents may not process fat adequately

A

Fatty tissues should be sampled and cut thinly for easy reagent action. Ethanol is a poor fat solvent. To ensure complete dehydration, a far better lipid solvent (acetone or isopropanol) should be inserted before using the final absolute ethanol

61
Q

Hard, dense tissues
Reason:

A

Tough keratin component of certain tissues

62
Q

Remedy for: Tough keratin component of certain tissues

A

Treat fixed tissues using 4% aqueous phenol for 24-72 hrs to soften

63
Q

On embedding, tissue is soft and mushy in the center
Reason:

A

Inadequate processing due to very thick or fatty sections

64
Q

Remedy: Inadequate processing due to very thick or fatty sections

A

At gross, cut thin sections especially fatty tissues, ensure complete fixation

histopathology lecture (5 decks)

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