A simple method for generating multitissue blocks without special equipment.

The idea of multitumor block to expedite simultaneous analysis of multiple tissue specimens was pioneered by Battifora, and several variations have been published since then. More recently, microarray technology has been introduced to allow placement of up to several hundreds specimens in 1 block using manual or automated sampling devices. This paper reports a manual technique for preparation of a multitissue block. Generation of such blocks requires no special equipment, and flexible block design is possible depending on nature of available material and desired sample size. The first step is dissection of cubical or rectangular samples from paraffin blocks or processed tissue with a razor blade or scalpel. The tissue pieces can be tattooed on cut surface with a permanent marker to facilitate orientation and identification. This marking is preserved during embedding until the block is cut. If a "deep" block is desired, the tissue can be turned 90 degree to provide a greater vertical depth. For embedding, the pieces are laid in paraffin bath in desired order, and when completely melted, they are placed into a deep embedding mold and organized in multiple rows (5 to 10 pieces/row). Scaffolding and control tissue pieces (eg, placental liver or intestinal tissue) can be added as desired. Horizontal or vertical empty space should be preserved to allow for more effective separation of ribbons upon cutting, preventing unnecessary sacrifice of sections. Such blocks can accommodate 30 to 60 cases depending on the tissue size, and they can potentially generate up to several hundreds of sections. This technique is especially suitable when abundant tissue is available, for example, generating blocks containing libraries of normal tissues or defined tumors for antibody screening or tumor immunophenotyping.