Lec 1 - Histopathology Video

Question 0

What occurs in the vacuum system?

Answer 0

The formalin fixed tissues will get exposed to graded higher concentrations of alcohol until dehydrated.

Question 1

Why is the tissue placed in 10% formalin?

Answer 1

To fix overnight- the formalin stops any further decay in the tissue and renders it to subsequent treatment for histopathologic processing

Question 2

What occurs after the alcohol ?

Answer 2

The alcohol in the tissue is replaced by xylene.

Question 3

What does xylene do?

Answer 3

Xylene is a solvent capable of dissolving paraffin.

Question 4

What occurs progressively?

Answer 4

Progressively the xylene is replaced by xylene/paraffin solutions as higher concentrations of paraffin is introduced

Question 5

What is the purpose of paraffin?

Answer 5

It renders it amendable to very thin slicing

Question 6

What is the usual tissue thickness?

Answer 6

4 and 8 micrometers

Question 7

What happens after the paraffin block is cooled?

Answer 7

It will be cut on a microtome with a sharp blade at 5 micrometer thickness.

Question 8

What happens after it is cut?

Answer 8

It is then placed on a warm water bath and picked up glass slides

Question 9

What must occur before staining can happen?

Answer 9

The tissue section must first be de-paraffinized and rehydrated so that aqueous stains can react. So the glass slides are passed thru xylene and then graded concentration of alcohol starting with 100% and ending with 70% solution .

Question 10

What is used after the 70%?alcohol?

Answer 10

Hematoxylin and eosin (H&E) is used.

Hematoxylin is a basic dye, that has affinity for acidic molecules such as DNA and RNA ( causing stain from dark blue to purple).

The red eosin is a acidic dye which has affinity for basic molecules such as proteins of cytoplasmic .it stains red cytoplasmic protein which lack a nucleus.

Question 11

What occurs after staining?

Answer 11

The tissue is protected for subsequent handling and archival filing. Therefore undergo dehydration thru increasing concentration of alcohol and clearing of xylene.

Question 12

What does the clearing of xylene allow?

Answer 12

This allows the introduction of a form of glue called permount. Permount will glue another piece of glass on top of the tissue . Permount also unify the optical density of the entire slide so it can be looked thru the tissue.

Question 13

What occurs lastly?

Answer 13

A diagnostic conclusion is reached based on a light microscope between 20 and 1000.

Question 14

What is seen at low magnification?

Answer 14

Normal mucosa has organized columns of glands

Abnormal mucosa has crowed abnormal aggregates of dark staining glands and are haphazardly arranged. Dark staining is due to increase number of cells in tumor. Hematoxylin causes tumor to stain darker

Question 15

What is seen at a slightly higher magnification?

Answer 15

A junction between normal and abnormal mucosa.

Abnormal has necrotic tissue because it is deprived of oxygen and nourishment and die.

Question 16

What is seen at higher magnification?

Answer 16

Normal- a single layer of columnar cells that have basally positioned nuclei and contain clear staining secretory material on luminal side.

Abnormal -multiple layers of haphazardly arranged cells . They have small amount of cytoplasm in relation to enlarged nuclei. Several mitoses are seen. This is malignant gland of colonic mucosa aka adenocarcinoma. Since it invading the muscle layer, it is invasive colonic adenocarcinoma