HISTOPATHOLOGY TECHNIQUES

HISTOPATHOLOGY TECHNIQUE

Histopathology techniques and the laboratory requirements

Introduction

Cells are the building blocks of all living things group of these cells unite to perform a special function. these group of cells are called tissue. the tissues of the body consists of large number of cells and they are classified according to the shape, size and functions of the cells. microscopic study of individual cells in a smear is called cytology and study of tissue is called Histology. ( refer post clinical biochemistry ) for the information on a cell and cell division.

HISTOPATHOLOGY TECHNIQUE

Histology is a department of anatomy that deals with the minute structure, composition and functions of tissues. Histopathology means the study of disease tissues. the pathologist responsible for the diagnosis of disease tissues is dependent on the technical skill of a histotechnologist, who prepares microscopic slides of the specimen the specimens slides should be well sectioned and properly stained to provide detailed information of the tissue under examination. histopathological studies have proved to be one of the most effective means in diagnosis tissue abnormalities is benign and malignant conditions.

HISTOPATHOLOGY TECHNIQUE

Exfoliative cytology, is concerned with the early detection of Cancer the malignant cell diffuse into the body fluid and secretions (exfoliate). the exfoliative cytological technique deals with the study of body fluid and secretions by director smear method and also by the study of concentrated materials. the various specimens used for exfoliative cytology are urine, sputum, vaginal and cervical smears, breast secretion etc. uterine cancer can be diagnosed from the study of vaginal secretions. similarly cancer of the urinary tract is diagnosed by the study of urine and breast cancer from the study of breast secretion through nipple. the presence of malignant cells in the body cavity fluids indicate involvement of serious membrane of particular body cavity such as peritoneum and pleura.

The histopathological specimens are mostly collected by a surgeon in an operation theatre. the specimens in the form of a small pieces of tissue are submitted to the histopathology section of a Pathology Laboratory. each specimen is immediately placed in a proper fixative and then it is entered in a log book (logging) and given identification number. a morphological description of the tissue is noted by the pathologist and following gross examination and internal examination of the tissue, a portion of the tissue is trimmed and handed over the to the store histotechnologist for laboratory processing.

The specimen processing includes the following basic step:-

1:- Fixing

When a tissue is removed from the body it begins to decompose. to preserve the nature state (as nearly as possible) the tissue is immediately placed into a solution called fixative and this process is called fixing.

2:-Embedding

To provide necessary hardness to cut sections.infiltration of paraffin wax is carried out. this process is called embedding, which involves

(a) removal of water by alcohol dehydration ,(b) infiltration of xylene or chloroform as a solvent for paraffin wax and

3:- Microtomy

Thin sections (slices) of the tissue are cut by using an equipment called microtome. this is performed when the paraffin is solidified and the tissue are ready in the form of blocks. these thin sections are then prepared for staining.

4:- Staining

The paraffin is removed from the section on the slide by drying and then by dewaxing. during dewaxing the section on the slide are treated first with xylene and then the section are rehydrated with ethyl alcohol in decreasing concentrations. the rehydrated sections are then stained by using appropriate staining methods.

5:- Mounting

After staining, the sections on the slides are dehydrated by treating with ethyl alcohol in increasing concentration and finally with xylene. by placing mounting medium such as Canada balsam and then by placing a cover slip on the mounting medium. The stained section on the slide are said to be mounted.

Laboratory requirement

Glassware

General glassware required in histopathology laboratory include pipettes,flask,beakers and reagent bottles which are also used in biochemistry laboratory refers clinical biochemistry. the other is special type of glassware required include the following:-

1:- Specimen containers (100 ml, 250 ml, and 500 ml wide mouth bottles).

2:- Coplin staining jars or dishes

3:- Balsam bottles

4:- Microscope slides and coverslips

Chemicals and reagents

Following are the various reagents and chemicals used in histopathology laboratory:-

1:- Fixatives

2:- Various organic solvents

3:- Decalcifying solutions

4:- Embedding related Chemicals and reagents

5:- Various staining solutions

6:- Various dilutions of ethyl alcohol

7:- Mountaining media,etc.

Note

Also refer chapters histopathology laboratory (clinical biochemistry) for information regarding the various Chemicals and reagents used in the histopathology laboratory.next chapter show,

Equipments and instruments

Gross station

Gross station is used for the gross examination of tissues received in the laboratory. the gross station should be equipped with the following facilities:-

Presence of exhaust duct.
Down draft exhaust ventilation.
Hood should be at the height of 3 feet from table top.
Arrangement of tube light and focus light.
Facility of ultraviolet germicidal light.
Arrangement of sink with two taps,with one tap attached with water spray gun with flexible pipe.
Arrangement of pull out tray writing.
A vertical support for mounting camera.
Different mould

Leukhartz 'L' ice,trays, paper boats,tissue tek base moulds are various moulds used for block making.

Wooden block for metal holders were attached to paraffin block as support for micrrotome attachment.

HISTOPATHOLOGY TECHNIQUES