Tissue array

Punching equipment from Beecher instruments (click for larger image)

History
Scientific work using this method was first published in 1998 (Kononen et al, 1998). In our lab. we started using tissue micro array in 2001. At present we have three internal projects in progress using tissue micro array. In addition we also cooperate with different other laboratories on scanning and scoring of arrays.

Description
The sampling of the original tissues for arraying is performed from morphologically representative regions of regular formalin-fixed paraffin-embedded tumour blocks. Analysis of a haematoxylin-eosin-section is necessary to localize the area of interest. Core tissue biopsies (diameter 0,6 mm, height 3-4 mm) are taken from individual donor blocks and arrayed into a new recipient paraffin block (35 x 23 mm) using a tissue micro arraying instrument (Beecher Instruments). The recipient block should not have any cracks or damage of any kind, and the paraffine surface should be cut plane using a microtome. We use 0,6 mm cylinders, and 0,4 mm spacing between cylinders. The donor block is manually positioned for sampling based on a visual alignment with the corresponding HE-stained section on a slide.

The position and identification of the biopsies are on advance registered in an Excel chart. These data are transferred to our software Patharray, and a map of the recipient block can be printed. The biopsies are placed in the recipient block in fields according to the map. Biopsies should be placed above the paraffin surface in the recipient block. Then all the biopsies will be represented in the first sections. When all the samples have been transferred to the recipient block, this is placed in a warm chamber at 37 ºC for at least 15 minutes. The paraffin has now become more flexible and it is possible to level the surface using a clean glass microscope slide. The biopsies will also adhere to the walls of the holes in the recipient block. After the construction is completed, the resulting tissue micro array block are cut with a rotation microtome (feed 4). These sections are put on water to stretch and are then picked up on DAKO slides. They are allowed to dry in room temperature and are then put in a heating chamber (60°) to make the paraffin sections stick to the glass slide. The arrays are then stained using haematoxylin or immunostaining.