1) Biopsy to Diagnosis / Histotechnique Flashcards
What is the first step in processing a biopsy specimen for histological examination?
Fixation is indeed the first step. Formalin (10% neutral-buffered formalin) is the most commonly used fixative.
What is the purpose of formalin in tissue preservation?
Fixation prevents tissue decomposition by cross-linking proteins and preserving tissue structure.
Why is paraffin embedding used, and what advantage does it provide?
Paraffin embedding provides structural support, enabling thin sectioning while preserving tissue morphology.
Describe the purpose of sectioning a tissue block and the typical thickness of sections used in histology.
The purpose of sectioning is to get a thin piece to be able to view the specimen properly. The typical thickness is 4–5 micrometers (μm) Thin sections are essential for light to pass through for microscopic examination.
What is the most common stain used in histology, and what structures does it highlight?
Hematoxylin and eosin (H&E) staining is the standard. Hematoxylin stains nuclei blue/purple, while eosin stains cytoplasm and extracellular proteins pink.
What does hematoxylin stain, and what color does it impart to these structures?
Hematoxylin binds to acidic structures (e.g., DNA in the nucleus), staining them blue or purple.
What does eosin stain, and what color does it impart?
Eosin stains basic/alkaline structures like proteins in the cytoplasm, imparting a pink colour.
What is Histology?
The microscopic study of the form and structure of normal tissue.
What is pathology?
The microscopic study of the form and structure of diseased tissue.
What is biopsy?
Small bit of tissue removed from patient for examination with microscope.
Why are margins examined in excised biopsy specimens, and how are they assessed histologically?
Margins are examined to ensure the lesion or tumor was entirely removed. Clear (negative) margins mean no tumor cells at the edges; positive margins indicate residual disease.
What is the process of biopsy to diagnosis?
Grossing > Fixation > Embedding > Microanatomy > H&E Staining > Pathologist review > IHC staining
What is immunohistochemistry (IHC), and how does it assist in diagnosing specific conditions?
IHC uses antibodies to detect specific antigens (proteins) in tissues, aiding in identifying cancers, infectious agents, or cellular markers.
What do you recall about Reticulin Stain?
Purpose:
Highlights reticulin fibers, which are composed of Type III collagen. These fibers form a supporting framework in soft tissues like the liver, spleen, bone marrow, and lymph nodes.
Appearance:
Reticulin fibers stain black due to the use of silver impregnation techniques.
Other tissue structures remain relatively unstained or light-colored, providing contrast.
Applications:
Detects structural changes in the stroma (e.g., fibrosis or architectural disarray).
Commonly used in the diagnosis of cirrhosis, bone marrow disorders, or certain tumors.
What do you recall about Trichrome Stain?
Purpose:
Differentiates between muscle, collagen, and other tissue components, making it useful for visualizing fibrosis or scarring.
Appearance (Masson’s Trichrome):
Collagen: Stains blue (or green, depending on the variant).
Muscle fibers: Stain red.
Nuclei: Stain black or dark purple.
Applications:
Identifies fibrosis in organs (e.g., liver, kidney, or heart).
Highlights scarring or connective tissue in diseases like myocardial infarction or chronic liver disease.
