Tissue microarray
Encyclopedia
Tissue (biology)
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
microarrays (also TMAs) consist of paraffin
Paraffin
In chemistry, paraffin is a term that can be used synonymously with "alkane", indicating hydrocarbons with the general formula CnH2n+2. Paraffin wax refers to a mixture of alkanes that falls within the 20 ≤ n ≤ 40 range; they are found in the solid state at room temperature and begin to enter the...
blocks in which up to 1000 separate tissue
Biological tissue
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
cores are assembled in array fashion to allow multiplex
Multiplex (assay)
A 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 analysis
Histology
Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is performed by examining cells and tissues commonly by sectioning and staining; followed by examination under a light microscope or electron microscope...
.
History
The major limitations in molecular clinical analysisClinical research
Clinical research is a branch of medical science that determines the safety and effectiveness of medications, devices, diagnostic products and treatment regimens intended for human use...
of tissues include the cumbersome nature of procedures, limited availability of diagnostic
Medical diagnosis
Medical diagnosis refers both to the process of attempting to determine or identify a possible disease or disorder , and to the opinion reached by this process...
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 tumorTumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
samples. These tissue cores are then inserted in a recipient paraffin block in a precisely spaced, array pattern. Sections
Histological section
Histological 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...
from this block are cut using a microtome
Microtome
A microtome is a sectioning instrument that allows for the cutting of extremely thin slices of material, known as sections. Microtomes are an important device in microscopy preparation, allowing for the preparation of samples for observation under transmitted light or electron radiation...
, 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 immunohistochemistry
Immunohistochemistry
Immunohistochemistry or IHC refers to the process of detecting antigens in cells of a tissue section by exploiting the principle of antibodies binding specifically to antigens in biological tissues. IHC takes its name from the roots "immuno," in reference to antibodies used in the procedure, and...
, and fluorescent in situ hybridization
Fluorescent in situ hybridization
FISH is a cytogenetic technique developed by biomedical researchers in the early 1980s that is 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...
. Tissue microarrays are particularly useful in analysis of cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
samples.