Role of Pathology in Diagnosis

Question 1

What is the most common benign breast neoplasm?

Answer 1

The most common benign breast neoplasm is a fibroadenoma.

Question 2

What is the most common malignant breast neoplasm?

Answer 2

The most common malignant breast neoplasm is a breast carcinoma.

Question 3

Give an example of a palpable difference between benign and malignant breast neoplasms.

What is the cause of this difference?

Answer 3

• Benign breast neoplasms are mobiel whereas malignant breast neoplasms are rarely mobile.
• This is because the malignant breast neoplasm is able to invade surrounding structures.

Question 4

List the tissue layers of the colon in order from superficial to deep.

In which layer of the colon do the majority of neoplasms arise?

Why?

Answer 4

1 - Mucosa.

2 - Submucosa.

3 - Muscularis.

4 - Serosa.

• The majority of colon cancers arise in the mucosa. This is because:

1 - It is the region exposed to the highest concentration of carcinogens.

2 - It is the region with the highest turnover rate.

Question 5

Which section of the colon is most commonly affected by colon carcinoma?

Answer 5

The sigmoid colon is the section of the colon which is most commonly affected by colon carcinoma.

Question 6

Why might colon cancer cause a change in bowel habit?

Answer 6

• Colon cancer can be stenosing.
• This can slow the passage of the stool through the colon, allowing for more time for water reabsorption, causing constipation.
• It can also obstruct solid matter from passing through the colon whilst permitting liquids to pass, causing diarrhoea.

Question 7

Which section of the colon is most commonly affected with a colon carcinoma that causes a change in bowel habit?

Why?

Answer 7

• Colon carcinomas affecting the sigmoid colon more commonly cause a change in bowel habit.
• This is because colon carcinomas of the sigmoid colon are more frequently stenosing, whereas colon carcinomas in the ascending colon are more frequently polypoid.

Question 8

List 3 biopsy techniques.

For each technique, give an example of an area of the body for which the technique is commonly used.

Answer 8

1 - Endoscopic biopsy (e.g. GI tract and bronchi).

2 - Needle biopsy (many areas).

3 - Punch biopsy (e.g. skin).

*These can all be used to obtain specimens to investigate cancer.

Question 9

List 4 techniques that are used to obtain cytology specimens.

Answer 9

1 - Smears.

2 - Endoscopic brushings.

3 - Bodily fluids.

4 - Fine needle aspiration.

*These can all be used to obtain specimens to investigate cancer.

Question 10

List 4 purposes of pathological assessments of cancer.

Answer 10

1 - To confirm the diagnosis of a malignancy.

2 - To determine the aggressiveness (grade) of a cancer.

3 - To assess the extent of spread (staging) of a cancer.

4 - To examine the completeness of excision.

Question 11

What is the most common distant site of spread of colorectal cancer?

Why?

Answer 11

• The most common distant site of spread of colorectal cancer is the liver.
• This is because the cancer is able to reach the liver directly by the hepatic portal vein.

Question 12

How can an inflammatory infiltration be told apart from a neoplastic infiltration histologically?

Answer 12

• An inflammatory infiltration consists of a mixed population of cells.
• A neoplastic infiltration consists of a pure population of cells.

Question 13

How are T lymphocytes told apart from B lymphocytes on a tissue specimen?

Answer 13

• T lymphocytes are tagged with CD3 antibodies.
• B lymphocytes are tagged with CD20 antibodies.
• The specimen is then examined using imaging.

Question 14

Give an example of an immunohistochemical prognostic marker for cancer.

How does it work?

Answer 14

• The Ki-67 labelling index is used as a prognostic marker for cancer.
• It detects various components of the cell cycle.
• The higher the labelling, the more rapid the turn over, indicating high metastatic potential.

Question 15

How can immunohistochemistry be used to identify therapeutic options for cancer?

Answer 15

• Expression of specific antigenic markers can be used to identify tumours that are likely to be amenable to specific therapies targeting the antigens expressed. For example:

1 - Breast carcinomas that express the growth factor HER2 can be treated with herceptin, a HER2 antagonist.

2 - Breast carcinomas that express the oestrogen receptor may be amenable to hormone therapy.

3 - GI stromal tumours expressing the tyrosine kinase receptor c-KIT can be treated with Gleevec, a tyrosine kinase inhibitor.

*Identifying mutations can also impact therapeutic options.

Question 16

List 2 examples of how fluorescence in-situ hybridisation (FISH) can be used to identify a neoplasm.

Answer 16

1 - FISH can be used to identify kappa and lambda light chains to demonstrate clonality in plasma cell infiltrates (this can also help tell apart an inflammatory from a neoplastic infiltration). E.g. a neoplasm of B cells will have a whole population of only kappa or only lambda, whereas a normal population of B cells will be heterogeneous.

2 - FISH can be used to identify Epstein-Barr virus encoded RNAs (EBERs) to identify EBV-related neoplasms.

Question 17

What is post-transplant lymphoproliferative disease?

Answer 17

Some immunosuppressants taken by patients post-transplantation have the side effect of interfering with T cell function, enabling uncontrolled proliferation of EBV-infected B cells.