Histology Intro

Question 1

The histopathology department is the backstage of the hospital and has a very important function.
a) Mention three types of specimens that the histopathology laboratory receives. (3 marks)

Answer 1

i. Surgically resected specimen – removal or whole tissues or organs such as hysterectomy, mastectomy, nephrectomy etc.
ii. Biopsies – can be incisional (sample of the tumour, not completely excides) or excisional (complete excision of the tumour
iii. Curettage – scraping of tissue such as endometrial samples, prostate and skin lesions. These are

Question 2

b) Mention three important functions of the histopathology department. (3 marks)

Answer 2

i. Confirmation or Differential diagnosis of malignant and benign lesions – such as differential diagnosis of a breast lump – fibroadenoma, fibrocystic changes, malignancy.
ii. Guidance of treatment – most commonly through the use of immunohistochemsitry for instance, if a breast cancer is oestrogen receptor positive the patient can be given tamoxifen or other anti-oestrogen drugs.
iii. Monitoring of therapy – to determine the degree of regression after chemotherapy or radiotherapy

Question 3

c) What is a frozen section and how is it done? (5 marks)

Answer 3

A Frozen section is used to process fresh, unfixed specimen in freezing temperatures to obtain a frozen block which is cut in the cryostat and can be processed as normal.

i. The patient identification is confirmed and goss examination is performed
ii. In the cryostat, OCT is placed on the chuck and on the cryobar boost
iii. Once completely frozen, the specimen placed on the OCT and allowed to freeze around the section and more OCT is placed on top.
iv. The specimen is sectioned using the microtome in the cryostat and placed onto clean glass slides
v. The slide is stained using progressive haematoxylin and eosin stain and observed under microscope

Question 4

d) Mention five indications for a frozen section and discuss the disadvantages of this investigation. (10 marks)

Answer 4

i. Intraoperative consultation – to determine whether the lesion is malignant and therefore, it should be remove
ii. Confirm clearance of resection margin - determine if the tumour touches the resection margin or not. Therefore, it guides the surgeon to remove more of the tumour or not.
iii. Confirm the suspected metastasis that was detect on radiology and guide therapy
iv. Confirm the type of tissue remove e.g. parathyroid gland can be difficult to distinguish from thyroid gland and requires histology for confirmation
v. Skin biopsy for immunofluorescence as normal processing will disrupt the staining pattern of IMF.

Disadvantages:
• Time taken to issue the report is very limited and also time to process – as the time to produce a frozen section is limited because it needs to be done immediately since they are not fixed and will start to deteriorate resulting in incorrect diagnosis as well
• Lack of special stains that can be performed during intraoperative procedures – mostly just haematoxylin and eosin as there is not time to carry out other stains.
• Decreased amount of consultation when compared to normal processing – especially when only one pathologist is available on the day
• Freezing artefacts – water can expand on freezing due to expenditure leading to ice crystals which can impair diagnosis, compression artefacts and nuclear chromatin changes can also be obtained.

Question 5

81. Mention four special stains and their use.

Answer 5

1. Trichrome stain (Masson’s trichrome stain) – to identify collagen and differentiate it from other eosinophilic structures seen with haematoxylin and eosin stains. This will help with investigating tissue injury and identify increase in collagen especially in liver which is indicates liver cirrhosis.
2. Reticulin stain – stains reticular fibres by silver impregnation to observe parenchymal structure of liver and spleen. This will allow observation of the architecture and confirm fibrosis, necrosis or increased proliferation of cells.
3. Periodic acid Schiff - Stains complex carbohydrates a deep red colour and can be used with diastase to differentate glycogen stores. The section that is not treated with diastase will stain glycogen stores but the slide that is, the glycogen stored are digested and these are not stained. Therefore, can be used to differentiate diseases such as alpha-1-antitrypsin disease as there will be accumulation of alpha-1-antitrypsin globules in the hepatocytes and these, like glycogen are PAS+. However, unlike glycogen these globules are resistant to diastase and remain positive even in digested sections (PAS/D).