ASCP HTL flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

10% neutral buffered formalin

A fixative containing about 4% w/v formaldehyde in phosphate buffer at pH 7.0-7.4; it is the standard routine fixative for paraffin sections.

Formalin penetration rate

Formalin penetrates tissue at approximately 1 mm per hour, so blocks are usually trimmed to 3-4 mm thick to allow complete fixation in a reasonable time.

Bouin solution pigment removal

Bouin fixative contains picric acid and leaves yellow color; lithium carbonate or saturated alcohol removes the yellow pigment before staining.

Mercury pigment removal

Zenker and B5 fixatives contain mercury and can leave brown-black pigment; iodine followed by sodium thiosulfate removes it.

Processing sequence

Routine tissue processing is dehydration in graded ethanol, clearing in xylene or a substitute, and infiltration with molten paraffin.

Paraffin section thickness

Routine paraffin sections for H&E are cut at 3-5 µm; immunohistochemistry sections are often cut at 3-4 µm.

Microtome clearance angle

The clearance angle between blade and block is usually 5-10 degrees; too small causes chatter, and too large causes scraping.

EDTA decalcification

EDTA is a chelating decalcifier that is slow but preserves antigens and nucleic acids better than acid decalcifiers.

Hematoxylin staining property

Hematoxylin is a basic dye that stains nucleic acids blue-purple, producing the nuclear detail in routine H&E sections.

Eosin staining property

Eosin is an acidic dye that stains proteins and cytoplasm pink to red; eosin Y is commonly used at pH 4-5.

Bluing after hematoxylin

Bluing in weakly alkaline water such as Scott's tap water or ammonia water converts hematoxylin from red to blue.

Progressive versus regressive

Progressive hematoxylin is stained to final intensity without differentiation; regressive hematoxylin is overstained and then differentiated in acid alcohol.

PAS with diastase

PAS stains glycogen and other carbohydrates magenta; diastase digestion removes glycogen, so loss of staining distinguishes glycogen from mucin.

Congo red amyloid

Congo red stains amyloid deposits and produces apple-green birefringence when viewed under polarized light.

Prussian blue reaction

Prussian blue demonstrates hemosiderin iron as blue granules; it is used to identify iron deposition in tissue.

GMS fungal stain

Grocott methenamine silver stains fungal cell walls black against a green counterstain and is used to demonstrate fungi.

Heat-induced antigen retrieval

Heat-induced epitope retrieval commonly uses citrate buffer at pH 6.0 or Tris-EDTA at pH 9.0 to unmask antigens in formalin-fixed tissue.

DAB chromogen

DAB is a peroxidase chromogen that produces a brown, alcohol-insoluble precipitate; it is widely used in immunohistochemistry.

Endogenous peroxidase block

Hydrogen peroxide, usually 3%, is applied before peroxidase detection to block endogenous peroxidase and reduce false-positive staining.

IHC positive control

A positive control is tissue known to contain the target antigen; it verifies that the staining reagents and procedure worked.

Molarity formula

Molarity equals moles of solute divided by liters of solution; it is used to prepare precise reagent concentrations in the laboratory.

Beer-Lambert law

Absorbance is directly proportional to the concentration of the absorbing substance and the path length at a fixed wavelength.

Reagent labeling requirements

Reagent labels should include identity, concentration, preparation date, and expiration date to ensure traceability and safe use.

pH calibration buffers

pH meters are calibrated with fresh standard buffers, typically pH 4.0, 7.0, and 10.0, before measuring solutions.

Formaldehyde OSHA PEL

The OSHA permissible exposure limit for formaldehyde is 0.75 ppm as an 8-hour time-weighted average and 2 ppm as a 15-minute short-term limit.

Westgard rules

Westgard rules are QC decision rules applied to Levey-Jennings charts to detect random and systematic analytical error.

Chemical Hygiene Plan

The Chemical Hygiene Plan describes safe handling, storage, and disposal of laboratory chemicals and must be accessible to personnel.

Sharps disposal

Needles, blades, and broken glass must be placed in puncture-resistant sharps containers, not in biohazard bags.

Frozen section temperature

Frozen sections are usually cut in a cryostat at about -20 to -25°C; temperature and freezing method affect section quality.

Cytology Pap stain

The Papanicolaou stain is used for cytology and stains nuclei blue-purple and cytoplasm pink, orange, or green depending on cell type.

FISH definition

Fluorescence in situ hybridization uses fluorescent DNA probes to detect gene amplifications, deletions, or translocations in cells.

Molecular specimen adequacy

Molecular tests require adequate cellularity and preserved nucleic acids; formalin fixation can degrade DNA and RNA over time.