Neoplasia

Question 1

What can basic pathological processes be classed as?

Answer 1

• Congenita anomalies – structural or functional
• Change sin cell growth or differentiation
• Degeneration and cell death
• Inflammation and healing
• Vascular disorders
• Neoplasia

Question 2

What are the 2 parts of a tumour that make up its name?

Answer 2

The cell types

Whether it is benign or malignant

Question 3

How can cells and tissues be basically classified?

Answer 3

Mesenchymal – cells that created connective tissues in the body.

Epithelial

Haematopoietic and lymphoid cells – cells of bone marrow that form the blood cells and associated lineages: erythrocytes, granulocytes, monocytes, macrophages and dendritic cells. Lymphoid is lymphocytes and plasma cells, as well as secondary and primary lymphoid organs.

Miscellaneous (everything else)

Question 4

What are some examples of cells of each basic classification?

Answer 4

Mesenchymal = fibroblast, endothelium, chondrocyte

Epithelial = urothelium, apocrine gland cell, squamous cells

Haematopoietic and lymphoid = lymphocyte, mast cell, plasma cell

Others = astrocyte, germ cell, Sertoli cell

Question 5

What is the nomenclature of mesenchymal cells?

Answer 5

Benign = -oma

Malignant = -sarcoma

Sarcoma is sometimes used to simply indicate a malignant tumour of mesenchymal origin, especially if the cell of origin is uncertain, such as a soft tissue sarcoma.

Question 6

What is the nomenclature of non-glandular epithelial tumours?

Answer 6

Non-glandular – epidermis and some mucosal surfaces, urothelium ad stratified squamous epithelial of the oral cavity.

Benign = papilloma

Malignant = carcinoma

Question 7

What is the nomenclature of glandular epithelial tumours?

Answer 7

Hepatocytes and renal tubular epithelial

Benign = adenoma

Malignant = adenocarcinoma or carcinoma

Carcinoma is sometimes used t simply indicate a malignant tumour of epithelial origin, especially if the cell of origin in uncertain, such as metastatic carcinoma.

Question 8

What are some examples of tumours named after their cell of origin?

Answer 8

Sertoli cell tumour

Interstitial (Leydig) cell tumour

Same for benign and malignant tumours

Question 9

What are some examples of tumours ending in -oma for both benign and malignant?

Answer 9

• Astrocytoma = astrocyte
• Oligodendroglioma = oligodendrocyte
• Seminoma = germ cell, testis
• Dysgerminoma = germ cell, ovary

Question 10

What are some examples of tumours ending in -oma different for benign and malignant?

Answer 10

Melanocytes: melanocytoma = benign and malignant melanoma = malignant

Question 11

Describe tumours of plasma cells and bone marrow.

Answer 11

Plasma cell (outside of bone marrow) = plasma cell tumour or plasmocytoma. Mostly benign.

Bone marrow = myeloma (malignant)

Question 12

What are some examples of tumours with malignant potential?

Answer 12

Lymphocytes in solid lymphoid organs/tissues = lymphoma, considered malignant

Bone marrow: erythroid, myeloid, lymphoid = leukaemia and may have detectable neoplastic cells circulating in the blood

Question 13

Outline the stages of identifying a tumour’s origin and if its benign or malignant.

Answer 13

1. Clinical history
2. Clinical examination
3. Possible imagine studies – location, evidence and if there is any metastasis
4. Microscopic examination – cytology or histopathology
5. Molecular analysis – little used in veterinary medicine right now but is sure to increase in the future

Question 14

List the gross features that could identify a tumour as benign or malignant.

Answer 14

Rate of growth
Tissue invasion
Metastatic spread

Question 15

How can growth rate identify a tumour as benign or malignant?

Answer 15

Broadly, the faster a tumour growth, the more malignant it is.

• However, not all malignant tumours are fast growing and not all benign tumours are slow growing. For example, cutaneous histiocytoma in dogs is a rapidly growing skin tumour.
• So this must be used with other features, not just by itself.

Question 16

How can tissue invasion be used to identify a tumour as benign or malignant?

Answer 16

• Invasive behaviour is a feature of malignancy
• Upon palpation, it is not demarcated and it is fixed in position

Question 17

How can metastatic spread be used to identify a tumour as benign or malignant?

Answer 17

If present, provides unequivocal evidence of malignancy.

Question 18

Describe the possible routes of metastatic spread.

Answer 18

Tumours may metastasise through 3 routes:
- Haematogenous (spread via blood vessels)
- Lymphatic
- Direct seeding in cavities (such as ventricular system or brain)

For example, a malignant tumour in the spleen may spread via the blood supply: from the spleen > splenic vein > portal hepatic vein > liver, so metastatic spread to the liver may be likely. If they enter the splenic lymphatics, they will spread to the lymph nodes and so these could also be a site of metastatic tumour spread. Although less common, it is possible that the tumour cells may break off or become detached from the splenic tumour and spread within the peritoneal cavity.

Question 19

How can the degree of differentiation be used to identify if a tumour is benign or malignant?

Answer 19

• How much the tumour resemble the tissue of origin.
• Well differentiated is when the cells have retained their specialist features
• Typically, neoplastic cells of benign tumours are well differentiated.
• Undifferentiated/anaplastic cells have loss of normal architecture/morphological features. This is generally a feature of malignancy.
• But not all malignant tumours have poorly differentiated cells.

Question 20

What is pleomorphism and how is it used to identify if a tumour is benign or malignant?

Answer 20

• Pleomorphism – variation in the size and shape of cells and/or nuclei. So cellular or nuclear pleomorphism are features of malignancy.
• Anisocytosis – greater than normal variation in cell size.
• Anisokaryosis – greater than normal variation in nuclear size.
• Anisocytosis and anisokaryosis are both things that can be associated with malignancy.

Question 21

What is the of nuclear changes in tumour cells and some examples of changes?

Answer 21

Increased proliferation and metabolic activity puts increased demand on the cell and the nucleus, causing other changes to the nucleus as well, commonly seen in malignancy:

• Increased nuclear size
• Large nucleoli
• Multiple nucleoli
• Coarse chromatin and hyperchromasia (nucleus stains darker basophilic)
• Increased mitotic figures
• Abnormal mitotic figures

Question 22

Describe the histopathological examination of benign tumour cells.

Answer 22

• Typically form masses composed of cells that are cohesive and stick together to form one discrete mass.
• Grows by expansion, which can sometimes result in compression of surrounding tissues and formation of a fibrous capsule.
• Tumour has well demarcated margins with no evidence of cells peeling off and invading into the surrounding tissues.

Question 23

Describe the histopathological examination of malignant tumours.

Answer 23

• Can show invasion and destruction of the surrounding tissues.
• Neoplastic [apocrine cells] are surrounded by connective tissue stroma, containing lots of fibroblasts producing collagen.
• These calls have been induced and conscripted by the tumour cells to form part of the tumour mass.
• This causes some malignant tumours to feel tough and hard.

Question 24

How can cell of origin be determined for a full tumour diagnosis?

Answer 24

• Imagine can find site of primary tumours
• Microscopic examination to identify origin
• Trying to identify tumours with poorly differentiated cells:

Question 25

How can tumours with poorly differentiated cells be diagnosed?

Answer 25

Cell shape = building blocks

Arrangement of cells = architectural features

Question 26

Describe the spindle basic shape of tumour cells.

Answer 26

Usually mesenchymal origin. Often aligned with the cells forming interwoven stream or bindles of cells aligned in different directions. May also form whirling patterns, sometimes round blood vessels.

Question 27

Describe the epithelioid cell basic shape.

Answer 27

Epithelial origin. Often retain some of their intercellular connections such as desmosomes. Because the cells are often joined together, they may often form chains or chords. May also form glandular like rings of cells called acini, often glandular epithelial origins.

Question 28

Describe round cell basic shape.

Answer 28

Included lymphocytes, plasma cells, mast cells and histiocytes origin. Often form discrete round or oval shaped, that may be arranged in sheets, densely or loosely packed.

Question 29

What are the direct physical effects that the tumour has on the host?

Answer 29

• Space occupying and compressive effects – can lead to dysfunction of organs and tissues.
• Obstructive effects if tumour originates within the walls of tissue or organs.
• Ulceration and destruction of tissues
• Haemorrhage

Question 30

What are paraneoplastic syndromes?

Answer 30

Indirect effects of tumours on the host. These occur when there is alteration in the structure or function of cells. There are 2 general mechanisms that underlie these.

Question 31

What are the 2 mechanisms that underlie paraneoplastic diseases?

Answer 31

Development of host immune responses against antigens expressed by the tumour. Results in cross-reactive immune responses against normal host tissues. Can cause development of immune mediated diseases.

Tumour produces biologically active substances, such as hormones, cytokines and peptides, that are released into the circulation.

Question 32

Explain pseudoparathyroidism as an example of a paraneoplastic syndrome via the biologically active substances mechanism.

Answer 32

• Some tumours produce a parathyroid hormone related peptide.
• Acts like parathyroid hormone and can cause hypercalcaemia.
• This is called humoral hypercalcaemia of malignancy/pseudohyperparathryoidism
• Associated with a range of tumour types but most commonly associated with lymphomas and carcinomas arising from the apocrine glands in the wall of the anal sacs in dogs.

Question 32

Explain pseudoparathyroidism as an example of a paraneoplastic syndrome via the biologically active substances mechanism.

Answer 32

• Some tumours produce a parathyroid hormone related peptide.
• Acts like parathyroid hormone and can cause hypercalcaemia.
• This is called humoral hypercalcaemia of malignancy/pseudohyperparathryoidism
• Associated with a range of tumour types but most commonly associated with lymphomas and carcinomas arising from the apocrine glands in the wall of the anal sacs in dogs.