Tissue microarrays (also
TMAs) consist of
paraffinIn chemistry, paraffin is the common name for the alkane hydrocarbons with the general formula CnH2n+2. Paraffin wax refers to the solids with 20 ≤ n ≤ 40 ....
blocks in which up to 1000 separate
tissueTissue is a cellular organizational level intermediate between cells and a complete organism. Hence, a tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function...
cores are assembled in array fashion to allow
multiplexA multiplex assay is a type of laboratory procedure that simultaneously measures multiple analytes in a single assay. It is distinguished from procedures that measure one or a few analytes at a time...
histological analysisHistology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is performed by examining a thin slice of tissue under a light microscope or electron microscope...
.
History
The major limitations in molecular
clinical-Medicine:* Clinical medical practice* Clinic* Illness* Clinical waste, segregated for safety or security* Clinical medical professions* Clinical psychology* Clinical examination; see Physical examination...
analysis of tissues include the cumbersome nature of procedures, limited availability of
diagnosticIn medicine, diagnosis is a label given for a medical condition or disease identified by its signs, symptoms, and from the results of various diagnostic procedures...
reagents and limited patient sample size. The technique of tissue microarray was developed to address these issues.
Multi-tissue blocks were first introduced by H. Battifora in 1986 with his so called “multitumor (sausage) tissue block" and modified in 1990 with its improvement, "the checkerboard tissue block" . In 1998 J. Kononen and collaborators developed the current technique, which uses a novel sampling approach to produce tissues of regular size and shape that can be more densely and precisely arrayed.
Procedure
In the tissue microarray technique, a hollow needle is used to remove tissue cores as small as 0.6 mm in diameter from regions of interest in paraffin-embedded tissues such as clinical biopsies or
tumorA tumor or tumour is the name for a swelling or lesion formed by an abnormal growth of cells . Tumor is not synonymous with cancer. A tumor can be benign, pre-malignant or malignant, whereas cancer is by definition malignant....
samples. These tissue cores are then inserted in a recipient paraffin block in a precisely spaced, array pattern.
SectionsHistological section refers to thin slices of tissue applied to a microscopic slide, usually around 5 to 10 micrometres thick, which are viewed under a microscope.Sections are usually stained with dyes to give optical contrast before viewing....
from this block are cut using a
microtomeA microtome is a mechanical instrument used to cut biological specimens into transparent thin sections for microscopic examination. Microtomes use steel, glass, or diamond blades depending upon the specimen being sliced and the desired thickness of the sections being cut. Steel blades are used to...
, mounted on a microscope slide and then analyzed by any method of standard histological analysis. Each microarray block can be cut into 100 – 500 sections, which can be subjected to independent tests. Tests commonly employed in tissue microarray include
immunohistochemistryImmunohistochemistry or IHC refers to the process of localizing antigens in cells of a tissue section exploiting the principle of antibodies binding specifically to antigens in biological tissues. It takes its name from the roots "immuno," in reference to antibodies used in the procedure, and...
, and
fluorescent in situ hybridizationFISH is a cytogenetic technique used to detect and localize the presence or absence of specific DNA sequences on chromosomes. FISH uses fluorescent probes that bind to only those parts of the chromosome with which they show a high degree of sequence similarity...
. Tissue microarrays are particularly useful in analysis of
cancerCancer is a class of diseases in which a group of cells display uncontrolled growth , invasion , and sometimes metastasis...
samples.
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