Cellular Science and Tissue Pathology 16
Cellular Science Lecture Notes
Lecture Structure and Content Overview
The lecture is structured into three main sections, originally part of tissue and tumor science, now integrated into the biomedical science module.
aims to cover gross structure, ultrastructure of normal cells, and disease-related changes,
Cell preparation methods are introduced and staining elements, visualization techniques and reproductive science will also be explored.
Cellular Science: Definition and Scope
Cellular science, or cellular pathology is defined as a hands-on discipline focused on studying tissues and cells (cytology).
It includes reproductive science, covering andrology, embryology, and related areas.
The field involves visual analysis and interpretation, offering more subjectivity compared to number-based disciplines like blood sciences and biochemistry.
Tissue Organization: Recap
Basic tissue organization reminder:
Cells form tissues, tissues form organs, organs form organ systems, and organ systems form organisms.
Four major tissue types: epithelial, connective, muscle, and nervous.
Epithelial Tissue
Histology primarily focuses on epithelial tissues due to the prevalence of abnormalities, particularly cancers, in these tissues.
Epithelial tissues line surfaces or are found in glandular tissue.
Endothelial cells, which line blood vessels, are an exception and not classified as epithelial.
Connective, Muscle and Nervous Tissue Types
Connective tissues, muscle, and nervous tissues are also examined in cell pathology.
Epithelial Cell Classification
Epithelial cells are described based on microscopic appearance, including the number of layers and cell shape.
Simple: Single layer.
Stratified: Multiple layers.
Pseudostratified: Appears multilayered but is a single layer (nuclei are not aligned).
Squamous: Flat cells.
Cuboidal/Columnar: More rectangular or cuboidal shapes.
Transitional Epithelium: Found in the bladder, changes shape to accommodate volume changes.
Tissue Structure and Function
The structure of a tissue is closely related to its function. For example, squamous cells in the skin are flattened and dead in the outer layer (unless affected by diseases like psoriasis).
Ciliated Cells
Ciliated cells, which are found in the GI and respiratory tracts, have cilia that aid in moving substances along the cell surface. These work with goblet cells that produce mucin.
Connective Tissue Types
Connective tissues examined in cellular science include:
Bone (specialist area).
Cartilage.
Adipose.
Loose connective tissue fibers.
Blood (primarily handled by haematology, but bone marrow may be examined in conjunction with haematological investigations).
Muscle Tissue
Muscle tissue types:
Smooth muscle (involuntary control; e.g., intestines).
Cardiac muscle (involuntary control).
Skeletal muscle (voluntary control).
All muscle types have layered cells with fibers; cytoplasm appears pinky-red, and nuclei are dark purple.
Nervous Tissue
Nervous tissue analysis is usually performed in specialist centers. Specimens may include whole brains, parts of brains, spinal cords, and peripheral nerves (though less common).
Whole brains are handled carefully due to Human Tissue Act considerations and potential delays to funeral processes.
Specimens are often post-mortem and require specialized preparation.
Disease Processes
Basic disease processes investigated include:
Neoplastic diseases (benign or malignant).
Inflammatory (though not a primary focus, may be present in tumour specimens).
Degenerative diseases.
Each category involves specific specimen types, with neoplastic diseases constituting the bulk of histology work.
Human Tissue Act and Specimen Handling
Specimens are obtained with consent and used for scheduled purposes such as disease diagnosis.
The Human Tissue Act covers tissues, while sperm, eggs, and oocytes are covered by the Human Embryological Act.
Relevant material includes cellular components; extracted DNA is not.
Rules differ for specimens from living versus deceased individuals.
Specimens can range from small biopsies to amputation specimens.
Specimen Types and Preparation
Skin Biopsies
Skin is a large portion of histology workload.
Punch biopsies use a small coring tool to remove a tissue sample.
Excisional biopsies remove larger areas, often with sutures to maintain orientation.
Analysis involves examining skin layers, especially in cases of malignant melanoma, to assess invasion.
Breast Specimens
Breast specimens (biopsies, lumpectomies) are inked to indicate specimen orientation for margin assessment.
Clear margins indicate no remaining cancer cells; unclear margins may require further surgery.
This approach aims to preserve breast tissue when possible.
Ovarian Cysts
Ovarian cysts vary in size and are examined for malignancy which are mostly fluid- filled, but some contain teratomas.
Prostate Chippings
Prostate chippings from individuals with benign hyperplasia are removed to relieve urinary obstruction.
Femoral Heads
Femoral heads from hip replacements or tumors undergo specialized bone histology. not routine
Teratomas
Teratomas, which occur in ovaries or testes, contain differentiated tissues like hair and teeth. They are usually benign but can be malignant.
Cytology
Cytology is a specialist area that may be part of or separate from the histology lab.
Specimens include fine needle aspirations, brushings, imprints, and cavity fluids.
Cytology samples are generally considered less invasive than tissue biopsies.
Cytology Specimens and Collection
Common cytology specimens include:
Fine needle aspirations.
Brushings from areas like the cheek or cervix.
Imprints (tissue pressed onto a slide).
Cavity fluids, such as pleural, peritoneal, or pericardial washings.
Bronchial washings.
While considered less invasive than surgical biopsies, they are still more invasive than routine blood tests.
Specimen Journey
Specimens arrive at the pathology lab, where they are booked in and assigned a tracking number.
Fixation occurs in fixative, with time varying based on specimen type.
Dissection is performed by a pathologist, assisted by a biomedical scientist.
Selected regions are placed in cassettes and processed automatically.
Biomedical scientists embed and section specimens, stain them, and perform quality control checks.
A pathologist makes the final diagnosis.
Intraoperative specimens follow an expedited process for quick results during surgery, using freeze-fixation and liquid nitrogen. Tissue quality may be lower than in standard processing.
Cytology Specimen Preparation: Smearing
Cytology specimens are often smeared on slides, which can result in contamination with mucus or blood.
Liquid-based cytology techniques can reduce these contaminants.
Smears must be properly prepared to avoid cell damage or clumping.
Slides are fixed in alcohol and allowed to air-dry before further processing.
Cytology Applications
Cytology is useful for:
Cancer screening and diagnosis.
Providing information for prognosis.
Assisting in treatment decisions.
Monitoring treatment effectiveness.
Certain elements, such as stains, can help determine appropriate treatments.
Applications: Inflammation
Histology and cytology are used in the diagnosis of chronic inflammatory conditions.
Special stains help identify microorganisms.
Fungal hyphae, for example, can be seen in cytology specimens, though specific species cannot be determined.
Applications: Autoimmune and Degenerative
Histology can aid in diagnosing autoimmune skin conditions and kidney diseases.
Neurodegenerative disorders like amyloidosis can be identified through histology, both pre- and post-mortem.
Bone histology is used for conditions like osteoporosis and bone metabolism disorders.
Reproductive Science
Cellular pathology includes reproductive science, which involves investigating:
Tumors of the reproductive tissue.
Products of conception (with caution regarding fetal remains due to legislation).
Placenta and umbilical cord samples.
Tubes from ectopic pregnancies.
Fetal Remains
Fetal remains should not be in the histology lab due to legislation, however, accidental inclusion may occur. These samples must be treated with dignity and respect.
Embryology and Andrology
Embryology and andrology are separate disciplines often pursued by those with a cellular pathology and histology background.
Molar Pregnancies
Molar pregnancies involve abnormal placental growth with cysts. There are two types:
Complete Mole: Two sets of paternal genes, no maternal genes, no fetus.
Partial Mole: One maternal set, two paternal sets, may have early fetal forms but not viable.
Microscopic Evaluation:
Molar pregnancies are investigated under histology because they can rarely lead to cancer, such as trophoblastic disease or choriocarcinoma.
Trophoblastic Disease
Trophoblastic disease can occur after any type of pregnancy and involves invasive placental cells. It is treated with radiotherapy and chemotherapy, with a generally good prognosis.
Embryology & ART
If interested in ART, embryology or andrology career, one would be helping individuals who cannot conceive naturally through procedures like in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI).
ICSI
Intracytoplasmic sperm injection (ICSI) is the process of injecting a sperm directly into an egg for fertilization, the culturing of up the embryos, grading them according to their quality, and then preserving any that werenât going to be implanted back into the individual.
Andrology
Andrology is a part of the fertility and includes:
spermatogenesis (the process of sperm cell development)
semen analyses
sperm function
fertilisation
contraception
cryopreservation ( preserving tissues by cooling them to sub-zero temperatures)
post vasectomy checks