Introduction

Introduction ,Tissue processing & sectioning Professor Dr. Wahda M.T.Al-Nuaimy Department of Pathology College of Medicine University of Mosul 3rd October 2016

Pathology

pathology is the study (logoy) of suffering (patho). Pathology: is the branch of medical science that studies the causes , nature and effects of diseases“Disease: any abnormality in the structure and /or function of an organ or tissue.

Branches of pathology Immunopathology , Toxicology, Forensic pathology, Genetic medicine , Hematology,Histopathology , Microbiology , Chemical pathology and Cytology

Biopsy: examination of tissue taken from living body (gross µscopical examination). Autopsy Also known as a post-mortem examination . Is a procedure that consists of a thorough examination of a dead body to determine the cause and manner of death and to evaluate any disease or injury that may be present.

Types of biopsy Incisional biopsy: a portion of tissue from a large lesion is taken-only diagnostic Excisional biopsy: the entire lesion is removed with a margin of adjacent normal tissue-diagnostic & therapeutic. Punch biopsy: by biopsy forceps in the uterus ,cervix, oral cavity & esophagus.

4) Core needle biopsy: by wide bore needle used percutaneously for sampling of internal organs. 5) Curettage biopsy : for diagnosis of internal diseases e.g. curettage of endometrium as diagnostic proceder.

Handling of biopsy: Once a biopsy is taken, it should be put in plastic or metal container with adequate amount of fixative ( 10% formalin) which causes rapid denaturation of cellular proteins & prevents autolysis. It should be sent to the lab. with a request form including patient’ s name, age, sex, short clinical notes, type of biopsy, name of tissue submitted , findings of operation & provisional diagnosis.

Gross examination

General principles for gross examination: Proper identification & orientation of the specimen. Place the specimen on a cutting board & record all the following data Type of specimen Dimension ( in centimeters) Weight Shape Consistency Surgical margins whether included or not involved by the tumor.

Histopathological techniques Deals with tissue deals with preparation of tissue for histopathological examination, the aim of these technique is to preserve microscopic anatomy of tissues & to cut tissue in very thin sections( 4-5 microns) this is achieved by passing tissue in a series of process.


Tissue processing can be done manually or mechanically & includes the following processes Fixation. Dehydration. Cleaning. Embedding. Cutting. Staining.

1- Fixation Most fixatives act by denaturating or precipitating cellular proteins which form meshwork that hold other structures & prevent autolysis. The most widely used fixative is 10% formalin.


2- Dehydration Is removal of water molecules from tissues and is achieved by graded alcohol. 3- Cleaning Alcohol replace water in the tissues, removal of alcohol from tissues is by Xylene which creates empty tissue spaces to be infiltrated by wax.


4- Embedding with wax Paraffin wax is used for embedding of tissue which form tissue blocks after cooling . It can be trimmed into thin sections (4-5microns) using the microtom the sections are placed on glass slides and become ready for staining.


Hematoxylin & Eosin (H&E) is the most widely used stain in histopathology Nuclei appear dark blue. Collage & cytoplasm appear pink. Keratin appears pink to red.


Special stains PAS ( periodic acid schiff) stain for glycogen & mucin . Congo-red for amyloid. Sudan-black for fat. Gimsa stain for Helicobacter pylori.


H. pylori stained dark blue with Gimsa stain

Amyloid deposits stain orange-red with Congo Red stain

Cytology: is the study of normal & abnormal morphologic characteristics of human cells. e.g. fluid cytology , Pap smear from the uterine cervix , FNAC.

It allows rapid diagnosis of the nature of the lesion whether benign or malignant to decide the next step in surgery. All laboratory staff should be informed and all preparations should be completed before arrival of tissue.

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