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  2.  Tissue microarray (TMA) is a method used to evaluate numerous samples of tissue in a short time.  First introduced { Battifora (1986) }  Multiple tissue samples arranged in a single paraffin block
  3.  Microarray contains many small representative tissue samples from hundreds of different cases assembled on a single histologic slide  Allows high throughput analysis of multiple specimens at same time
  4.  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 tumor samples. These tissue cores are then inserted in a recipient paraffin block in a precisely spaced, array pattern.
  5.  Tissue microarrays are paraffin blocks produced by extracting cylindrical tissue cores from different paraffin donor blocks and re-embedding these into a single recipient (microarray) block at defined array coordinates.
  6.  Experimental applications  Clinical applications
  7.  Array comparative genomic hybridization (aCGH)  Genotyping  Sequencing  Genome tiling  Gene expression
  8.  Gene expression profiling as an ancillary diagnostic tool for the pathologist  Predicting disease behavior  Predicting survival  Predicting therapeutic response  Nontumor pathology
  9.  Genotyping  Genome copy number  Methylation  DNA sequencing
  10.  Amplification of a scarce resource  Simultaneous analysis of very large numbers of specimens  Experimental uniformity  Decreased assay volume, time and cost effective  Does not destroy original block for diagnosis and conserves valuable tissue
  11.  Used as quality control in H&E and IHC  Used for wide range of staining procedures, IHC, ISH, FISH, Special stains and H&E  Enable study and evaluation of many diseases(diagnostic tool)  In Clinical pathology as quality control for new antibodies
  12.  Tissue heterogenity  One of the most common criticisms of tissue microarray is that the small cores sampled may not be representative of the whole tumor, particularly in heterogenous cancers such as prostate adenocarcinoma and Hodgkin lymphoma
  13.  Determine which blocks will be arrayed  Mark the area of interest either on the slide or block  Both should be marked in same area  At least 1mm thick  If marked area< 1mm thick , two cores are stacked on top of each other
  14.  Color indicators: RED------------CANCER GREEN----------NORMAL BLACK----------PRE-INVASIVE
  15.  Four sizes:  0.6 , 1.0 , 1.5 , and 2.0mm General use Ideal spacing-----------0.1mm
  16.  Blank paraffin wax block  There should be no holes in the block caused by air bubbles  1.0mm needle preferred: gives a desireable core and leaves little distortion in donor block  Ensure the alignment of punches
  17.  Smoothing and Sectioning  Microtomy  Troubleshooting and tips:  Core doesn’t come out easily, punch tip is bent, change it  Tissue core pushed too deep
  18.  Insufficient spacing of core  Thinning of cores in the block, uneven cores  Loss of tissue on water bath  Refacing block  Refacing angle