L13 - Pathology of Cancer - Classification of Neoplasms

Question 1

What is a neoplasm?

Answer 1

A mass of cells that:

1 - Have undergone an irreversible change from normality

2 - Proliferated in an uncoordinated manner

3 - Are partially or completely independent of the factors which control normal cell growth

Question 2

What is cancer?

Answer 2

A malignant neoplasm

Question 3

What are the requirements of a neoplasm to be considered malignant?

Answer 3

Malignant neoplasms have capacity for:

• Local invasion into surrounding tissue
• Spread to distant sites to form metastases

Question 4

Give an example of a neoplasm that behaves in an ‘intermediate’ manner.

Answer 4

• Basal cell carcinoma

- As it invades local tissues but doesn’t metastasise

Question 5

How do the tissues of origin of most malignant neoplasms and most benign neoplasms differ?

Answer 5

• Most malignant neoplasms originate from epithelial cells

- Most benign neoplasms originate from mesenchymal cells

Question 6

What is differentiation and how does it usually differ between benign and malignant neoplasms?

Answer 6

• Differentiation is the degree to which a neoplasm histologically resembles its tissue of origin
• Benign neoplasms are always well-differentiated
• Malignant neoplasms have variable differentiation

Question 7

What is an anaplastic neoplasm?

Answer 7

A very poorly differentiated malignant tumour in which it is impossible to determine the histogenesis

Question 8

What is the difference between staging and grading of neoplasms?

Answer 8

• Staging is used to measure the extent of spread

- Grading is used to describe the degree of differentiation

Question 9

Describe the naming system for benign and malignant neoplasms that originate from epithelial and mesenchymal tissues.

Answer 9

• The suffix for a benign neoplasm of squamous and transitional epithelial cells is papilloma
• The suffix for a benign neoplasm of glandular epithelial cells is adenoma
• The suffix for a malignant neoplasm of squamous and transitional epithelial cells is carcinoma
• The suffix for a malignant neoplasm of glandular epithelial cells is adenocarcinoma
• The suffix for a benign neoplasm of mesenchymal tissue is ‘-oma’
• The suffix for a malignant neoplasm of mesenchymal tissue is a sarcoma

Question 10

How are thyroid cancers classified?

Answer 10

• Thyroid cancers are classified on the basis of their histology. In descending order of both frequency and prognosis, classes include:

1 - Papillary

2 - Follicular

3 - Anaplastic

Question 11

What is a teratoma?

Answer 11

• A teratoma is a neoplasm derived from embryonic germ cells

- Teratomas have the capacity to form cells representative of all 3 germ cell layers (they are totipotent cells)

Question 12

Where do teratomas usually occur?

Answer 12

1 - Ovary (usually benign)

2 - Testis (usually malignant)

3 - Midline structures (behaviour variable)

Question 13

What is a blastoma?

Answer 13

• A blastoma is a neoplasm derived from multipotent embryonic blast cells
• e.g. nephroblastoma & hepatoblastoma

Question 14

What are hamartomas?

Answer 14

• Hamartomas are tumour-like malformations (not genuine neoplasms)
• Hamartomas stop growing when the host stops growing
• e.g. pigmented nevi (moles) & skin haemangioma

Question 15

List 5 differences in the gross appearance between benign and malignant neoplasms.

Answer 15

1 - Benign neoplasms are well circumscribed, whereas malignant neoplasms are irregular in shape

2 - Benign neoplasms are generally smaller in size, whereas malignant neoplasms are generally larger

3 - Benign neoplasms don’t usually haemorrhage, whereas malignant neoplasms commonly do

4 - Benign neoplasms don’t usually form ulcers, whereas malignant neoplasms commonly do

5 - Benign neoplasms don’t usually necrose, whereas malignant neoplasms commonly do

Question 16

What is pleomorphism?

Answer 16

• High variation in the size and shape of the cells and nuclei within a population of cancer cells
• This is characteristic of malignant tumours

Question 17

List 5 differences in the microscopic features between benign and malignant neoplasms.

Answer 17

1 - Benign neoplasms have a normal nuclear size, whereas malignant neoplasms have enlarged nuclei

2 - Benign neoplasms have small nucleoli, whereas malignant neoplasms have prominent nucleoli (usually expressed in terms of nuclear:cytoplasmic ratio)

3 - Benign neoplasms don’t usually show pleomorphism, whereas malignant neoplasms commonly do

4 - Benign neoplasms do not frequently undergo mitosis, whereas malignant neoplasms frequently undergo mitosis

5 - Benign neoplasms are well differentiated, whereas malignant neoplasms have variable differentiation