Fixation of breast tissue is an important process for preparing biological samples for laboratory examination. Performed on tissue from biopsies or surgeries, it ensures structural integrity. This is important for accurate medical diagnoses, especially in breast health.
Importance of Breast Tissue Fixation
Fixation prevents natural degradation of cells and tissues after removal from the body. Without it, samples rapidly undergo autolysis (self-digestion) and putrefaction (microbial decomposition). These processes distort cellular structures and compromise sample integrity.
Fixation stabilizes cellular components like proteins and nucleic acids by forming cross-links. This solidifies the tissue, preserving its structure close to its living state. Proper preservation allows pathologists to examine tissue under a microscope, identify abnormalities, and conduct further molecular tests, leading to a precise diagnosis.
The Process of Breast Tissue Fixation
The most common fixative for breast tissue is 10% neutral buffered formalin (NBF). Formalin forms chemical cross-links between protein molecules. This creates a stable network, solidifying components, halting enzymatic activity, and preventing microbial growth.
For effective fixation, fixative volume should be generous, ideally 10 to 20 times the tissue sample. This ensures adequate penetration. Fixation duration ranges from 6 to 72 hours, depending on tissue size and density. Thicker specimens (over 4mm) require longer times for full formalin penetration.
Fixation occurs at room temperature for optimal morphological preservation. Refrigeration slows fixation, potentially leading to incomplete preservation. Gentle agitation, especially initially, improves diffusion and ensures consistent exposure to fresh formalin, preventing localized poor fixation.
What Happens After Fixation: The Path to Diagnosis
After fixation, “grossing” involves macroscopic examination and precise tissue sampling. A pathologist or trained assistant inspects the specimen, noting its size, shape, color, and any visible abnormalities. The tissue is measured, described, and sectioned to select specific areas for microscopic analysis.
Following grossing, tissue undergoes processing. This begins with dehydration, removing water by immersing tissue in increasing alcohol concentrations. Next, a clearing agent, often xylene, replaces alcohol, making tissue transparent and receptive to embedding medium. The tissue is then infiltrated with molten paraffin wax, saturating the sample and providing structural support.
Once infiltrated, tissue is embedded into a paraffin block, carefully oriented within a mold of molten wax that solidifies upon cooling. This block is ready for microtomy, where a microtome cuts extremely thin sections (typically 4-5 micrometers thick). These sections are floated onto a warm water bath to flatten them and mounted onto glass slides.
Final steps involve staining tissue sections for microscopic visibility. Hematoxylin and Eosin (H&E) staining is routine; hematoxylin stains cell nuclei blue-purple, while eosin stains cytoplasm and extracellular matrix pink. Specialized immunohistochemical (IHC) stains may also be applied, using antibodies to detect specific proteins or biomarkers. These techniques allow pathologists to examine slides, identify cellular changes, and render a diagnosis.