Professional Practice in Biomedical Science – Histopathology

Histopathology: Definition & Importance

Histopathology is the microscopic study of diseased tissues. By examining very small samples taken from any body site, pathologists can quickly and cost-effectively explain a patient’s symptoms, confirm or exclude malignancy, and contribute decisive information for Multi-Disciplinary Team treatment planning.

Laboratory Scope & Staff

At the Royal Victoria Hospital (RVH) the Cellular Pathology Laboratory processes about 65\,000 specimens annually. The service integrates several subspecialties—Cytopathology, Immunohistochemistry, Immunofluorescence, Molecular and Neuropathology, Electron Microscopy, and Mortuary practice. Core staff include Consultant and Trainee Histopathologists, Biomedical Scientists, Associate Practitioners, Medical Laboratory Assistants, management, clerical, and archiving teams.

Sample Types & Rationale

Biopsies (3–8 mm cores or punches) provide an initial, minimally invasive diagnosis for infection, inflammation, benign change, autoimmune disease, trauma or cancer. Resections remove part or whole organs—e.g. hysterectomy, mastectomy, bowel or kidney resections—to treat or cure confirmed disease. Sources range from operating theatres and day clinics to GP and dental surgeries.

Fixation & Processing

Immediate fixation preserves tissue morphology once blood supply ceases. The gold-standard fixative is 10\% Neutral Buffered Formalin. Failure to fix leads to putrefaction (bacterial decay) or autolysis (enzymatic self-digestion). In-lab reception verifies patient identity (Minimum Acceptance Criteria) and logs each case to the Laboratory Information Management System. Dissection records colour, texture, weight and three-dimensional measurements.

Processing is fully automated: dehydration through graded alcohols (70\%–100\%), xylene clearing, and molten-wax impregnation under heat, vacuum and agitation. Embedding solidifies tissue in paraffin cassettes, enabling microtomy sections of 3{-}4\,\mu m—approximately one-cell thick.

Routine H&E Staining

Haematoxylin & Eosin (H&E) is the universal diagnostic stain. Dewaxed sections are regressed, differentiated and blued to show basophilic nuclei (blue-black) and eosinophilic cytoplasm / extracellular matrix (pink to red). Results are reproducible, inexpensive and easily automated.

Ancillary Testing

Diagnosis is refined by additional techniques:
• Special stains (e.g. Congo Red for amyloid, Perl’s for iron, PAS for glycogen) highlight specific molecules or pathogens.
• Immunohistochemistry (IHC) uses antibody–enzyme complexes (e.g. Universal DAB system) to demonstrate antigen expression; brown/black chromogen guides tumour typing, grading and prognostication (e.g. ER, PR, HER2 panels in breast cancer that direct tamoxifen or herceptin therapy).
• Immunofluorescence and Molecular tests further classify tumours, predict therapy response and detect tiny pathogens. Interpretation must integrate H&E with all ancillary results; no single test is definitive.

Role of the Biomedical Scientist

Biomedical Scientists oversee pre-analytical checks, dissection, processing, embedding, microtomy, staining, quality control and incident reporting. They ensure turnaround times, reagent safety, equipment maintenance and continual audit, supplying pathologists with high-quality slides and data crucial for accurate diagnosis, prognosis and therapy selection.

Key Takeaways

Histopathology provides the microscopic foundation for modern patient care. Accurate fixation, meticulous processing and appropriate staining—backed by skilled Biomedical Scientists—yield reliable diagnoses and guide personalised treatment plans.