Tissue MicroArray Basics

This document is aimed at people with a non-medical background who want to know some of the basics of Tissue MicroArrays.

Specimens & Blocks & TissueDiagnosis

A specimen is an organ that comes out of a patient during surgery.  Tissue from a specimen is cut off and placed into paraffin blocks.  A specimen generally yields many blocks.  Throughout this document, these types of blocks will be referred to as regular blocks or donor blocks. (*)

Blocks are cut into slides so that they can be viewed under a microscope.  Certain areas on the slide are circled and given a diagnosis.  For example circle A may be normal, and circle B may be cancer.  This sub-region on the block/slide is known as a tissueDiagnosis.  A block/slide may have several tissue-diagnoses. 

This process of creating specimens, blocks, and slides was done before Tissue MicroArrays were invented.  The process of creating Tissue Microarrays is described in the next section: Creating an ArrayBlock.

prostate specimen
A Prostate Specimen
A slide.  The yellow circle represents a tissueDiagnosis.  There may be several tissueDiagnosises per slide, and each is labelled, given a letter-designation (a,b,c,etc), and given a diagnosis (normal, cancer, etc)

Creating an ArrayBlock

An arrayBlock is created by taking tissue from regular (donor blocks), and placing them into a recipient block (the ArrayBlock) in an array format.  

block extration
arrayblock insertion
Step#1: A technician takes tissue from a block with a hollow cylinder tube.  Notice the techincian is taking the tissue from a special circled region on the block, a sub-block region known as the TissueDiagnosis, which is described above. 
Step#2: The technician transfers the tissue in the hollow cylinder to the appropriate coordinate in an ArrayBlock.

a block and an ArrayBlock
The  image represents how an ArrayCore (Cylinder) is taken from the block and then placed in a coordinate in the ArrayBlock.


Similar to a regular slide, an arraySlide is created by cutting an ArrayBlock and placing the thin layer of tissue on a slide.  An arrayBlock may yield several arraySlides.  In a sense, blocks and arrayBlocks are 3-dimensional, while slides and arraySlides are 2-dimensional.  Blocks and ArrayBlocks can not be viewed under a microscope, while slides and arraySlides can.  Once the arraySlide is obtained, a pathologist has the advantage of viewing the tissue of many blocks/specimens on the same slide.  Thus throughput is greatly improved. 

an arrayslide
An ArraySlide


the tma process
The image describes the process of creating a tissue microArrays.

ArraySlide Scanning Machines

There are machines available that will scan ArraySlide, and put the images into an electronic format. 

bliss machine
The BLISS Machine from BACUS labs.  Note the arraySlide in the microscope.

*A word on naming: Unless the word Array is used, you can always assume we are talking about normal, (donor) blocks.  So the word blocks will always refer to normal blocks, and the word ArrayBlock will always be used for Array (receipient) blocks. 

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