Tumor Pathology 1+2

Question 1

Describe the classification and nomenclature of tumours.

Answer 1

1. Histological Classification
   Carcinomas: Tumors that arise from epithelial cells. Subtypes include:
   Adenocarcinomas: Arising from glandular tissues.
   Squamous cell carcinomas: From squamous epithelial cells.
   Sarcomas: Connective tissue tumors, such as:
   Osteosarcoma: Bone tissue.
   Liposarcoma: Fat tissue.
   Leukemias: Blood cancers originating from hematopoietic cells in the bone marrow.
   Lymphomas: Cancers of the lymphatic system.
   Melanomas: Cancers arising from melanocytes, usually in the skin.
2. Behavioral Classification
   Benign Tumors: Non-cancerous growths that do not invade nearby tissues or spread to other parts of the body (e.g., lipomas, fibromas).
   Malignant Tumors: Cancerous tumors that can invade nearby tissues and metastasize to distant sites.
3. Grading
   Tumors are graded based on how abnormal the cancer cells look under a microscope. The grades range from:
   Grade I: Well-differentiated (closer to normal cells).
   Grade II: Moderately differentiated.
   Grade III: Poorly differentiated (more abnormal appearance).
   Grade IV: Undifferentiated (very abnormal).
4. Staging
   Staging describes the extent of cancer in the body and often uses the TNM system:
   T (Tumor): Size and extent of the primary tumor.
   N (Node): Involvement of regional lymph nodes.
   M (Metastasis): Presence of distant metastases.
5. Nomenclature
   Tumors are often named based on their tissue of origin combined with suffixes that indicate their nature. Common suffixes include:
   -oma: Typically indicates a benign tumor (e.g., adenoma).
   -carcinoma: Indicates malignant tumors of epithelial origin (e.g., adenocarcinoma).
   -sarcoma: Indicates malignant tumors of connective tissue origin (e.g., osteosarcoma).
6. Other Classifications
   Neuroectodermal Tumors: Including gliomas and neuroblastomas, arising from nerve tissue.
   Germ Cell Tumors: Arising from germ cells, often found in the testes or ovaries (e.g., teratomas).

Question 2

List the differences between benign and malignant tumours.

Answer 2

1. Growth Rate
   Benign Tumors: Typically grow slowly.
   Malignant Tumors: Often grow rapidly.
2. Invasiveness
   Benign Tumors: Generally remain localized and do not invade surrounding tissues.
   Malignant Tumors: Can invade nearby tissues and organs.
3. Metastasis

Benign Tumors: Do not metastasize (spread to distant sites).
Malignant Tumors: Can metastasize to other parts of the body through the bloodstream or lymphatic system.

4. Histological Appearance
   Benign Tumors: Cells often resemble normal cells and are well-differentiated.
   Malignant Tumors: Cells usually appear abnormal, poorly differentiated, and have a higher degree of atypia.
5. Capsule Formation
   Benign Tumors: Often encapsulated, making them distinct from surrounding tissues.
   Malignant Tumors: Typically not encapsulated, allowing for invasion into surrounding tissues.
6. Symptoms
   Benign Tumors: May cause symptoms depending on their size and location but are often asymptomatic.
   Malignant Tumors: Often cause symptoms related to their size, location, and metastasis, such as pain, weight loss, or organ dysfunction.
7. Recurrence
   Benign Tumors: Less likely to recur after removal.
   Malignant Tumors: More likely to recur after treatment.
8. Prognosis
   Benign Tumors: Generally have a good prognosis and are often not life-threatening.
   Malignant Tumors: Prognosis varies widely based on type, stage, and treatment, and can be life-threatening.
9. Treatment Approach
   Benign Tumors: May not require treatment unless they cause problems; surgical removal is often curative.
   Malignant Tumors: Typically require a combination of surgery, chemotherapy, radiation, or targeted therapies.

Question 3

Define the properties of cancer cells.

Answer 3

1. Uncontrolled Proliferation
   Cancer cells divide uncontrollably, leading to tumor formation. They often bypass normal regulatory mechanisms that limit cell division.
2. Loss of Contact Inhibition
   Normal cells stop dividing when they come into contact with other cells. Cancer cells can grow and divide even when they are densely packed.
3. Invasiveness
   Cancer cells can invade surrounding tissues and structures, breaking through the normal barriers that separate different tissue types.
4. Metastasis
   Cancer cells can spread from their original site to distant parts of the body through the bloodstream or lymphatic system, establishing secondary tumors.
5. Altered Cell Signaling
   Cancer cells often have changes in signaling pathways that allow them to grow and survive in conditions that would normally be unfavorable.
6. Immortality
   Cancer cells can evade normal cellular aging and death (apoptosis), allowing them to survive indefinitely and continue dividing.
7. Genetic Instability
   Cancer cells often have a high mutation rate and exhibit chromosomal abnormalities, leading to further genetic changes that promote malignancy.
8. Angiogenesis
   Cancer cells can stimulate the formation of new blood vessels (angiogenesis) to supply the growing tumor with nutrients and oxygen.
9. Altered Metabolism
   Cancer cells often exhibit changes in metabolism, such as increased glycolysis (the Warburg effect), allowing them to generate energy and support rapid growth even in low-oxygen conditions.
10. Immune Evasion
    Cancer cells can develop mechanisms to evade detection and destruction by the immune system, often by expressing certain proteins that inhibit immune responses.
11. Diverse Cell Characteristics
    Within a tumor, cancer cells can exhibit significant heterogeneity, with variations in properties such as growth rates, invasive potential, and responsiveness to treatment.

Question 4

Define the spread of cancer and its mechanisms.

Answer 4

1. Local Invasion
   Invasion of Surrounding Tissues: Cancer cells can invade nearby tissues by breaking down extracellular matrix components through the secretion of enzymes (e.g., matrix metalloproteinases).
   Migration: Cancer cells may move into adjacent tissues, leading to the destruction of normal cells and structures.
2. Intravasation
   Entering Blood Vessels or Lymphatics: Cancer cells can invade blood vessels or lymphatic vessels, allowing them to enter the circulatory system. This process is facilitated by alterations in cell adhesion molecules, which help them detach from the primary tumor.
3. Circulation
   Survival in the Circulation: Once in the bloodstream or lymphatic system, cancer cells may encounter challenges such as shear stress and immune surveillance. They can survive by forming aggregates with platelets or evading immune detection.
4. Extravasation
   Leaving the Bloodstream: Cancer cells exit blood vessels or lymphatics to invade distant tissues. This process often involves the cancer cells adhering to the endothelium (lining of blood vessels) and passing through the vessel wall.
5. Colonization
   Establishing Secondary Tumors: After extravasation, cancer cells can proliferate and form new tumors in distant sites. This step is often influenced by the microenvironment of the target tissue, which may provide favorable conditions for growth.
6. Angiogenesis
   Formation of New Blood Vessels: For secondary tumors to grow, they often require a new blood supply, which is facilitated by angiogenesis. Cancer cells can secrete growth factors (like VEGF) to stimulate the formation of new blood vessels.
7. Interactions with the Microenvironment
   Tumor Microenvironment: Cancer cells interact with the surrounding stromal cells, immune cells, and extracellular matrix, which can support their growth, survival, and ability to metastasize. Factors such as inflammation can also promote metastasis.