Lab. investigations L 2.pdf - L:2 Laboratory investigations...

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1Biopsy:A biopsy is a procedure to remove a piece of tissue or a sample of cells from the body so that it can be analyzed in a lab.Indications:1-Lesions which have neoplastic or premalignant features2-Lesions of uncertain etiology3-Persistantlesions failing to respond treatment4-Confirmation of clinical diagnosisLaboratory investigationsا.د.لﺿﺎﻓدﯾرﻐﺗL:2Types of biopsy:-1-Excisional2-Incisional3-FNA4- Thick (core) needle biopsy5- Exfoliative cytology6-Frozen section7-Oral brush biopsyIncisional is the removal of part of the lesion used to determine the diagnosis before treatmentExcisional biopsy is the removal of whole lesion used to confirm diagnosis
2During fine-needle aspiration, a long, thin needle is inserted into the suspicious area. A syringe is usedto draw out fluid and cells for analysis & smeared on slide, it is rapid & usually effective to diagnose of malignant from benign neoplasm although it is not completely conclusive.small size of the needle avoid damage to vital structure & it is valuable in case when incisional biopsy contra indicated as in pleomorphic adenoma or other types of malignant lesions in parotid glandDisadvantage: it require experience, small specimen may be unrepresentative, definitive diagnosis is not always possibleFine needle aspiration biopsyCore needle biopsy : A larger needle with a cutting tip is used during core needle biopsy to draw a column of tissue out of a suspicious area. the sample are larger than FNA & preserve architecture of tissue ,give more definitive diagnosis than FNA , but there is increase of the risk of seeding of neoplasm into the tissue & risk of damaging vital structures. It is used when incisional biopsy is inaccessible e.g. laryngeal tumor.Exfoliative cytology :which is the examination of cells scraped from the surface of a lesion , it is quick & easy ,no local anesthesia is required also special techniques such as immune-staining can be applied.it is useful in detection of virally damaged cells, acantholytic cells of pemphigues& candidalhyphae .But it provides no information on deeper tissue & has no value in diagnosis of cancer
3Frozen sectionsFrozen sections allows a stained slide to examined within 10 min of taking the specimen , the tissue is send fresh to lab. To be quickly frozen to about -70 c by liquid nitrogen or dry ice. section is cut on refrigerated microtome and stainedThe main advantage: is the time is too little so frozen section can be established at operation to determine whether tumor benign or malignant ,but the section appear deferent from fixed material , also freezing artifacts can distore the cellular picture ,and definitive diagnosis some times impossibleFixation of tissueUsually 10% formalin is used, procedure take about 24 hour, specimen should put in 10 time their volume because tissue make the fixative weaker as fixation proceedsAfter fixation tissue is dehydrated by the use of solvent & then impregnated in paraffin wax, the wax block is

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