From a historical perspective, there are millions of FFPE tissue blocks in storage and in use today; these range in age from being generated several decades ago to blocks prepared at the time of this writing. Block storage methodologies have typically been comprised of the following, although there are variations on the theme:
- Each FFPE Block is identified by applying handwritten or printed labels to the block/cassette-based on patient information. You can also look for ffpe block storage via http://www.geneticistinc.com/.
- Blocks are sorted numerically. As blocks from additional tissues for the same patient are generated at a later time, grouped blocks are re-sorted to accommodate the nested blocks.
- Blocks are archived on-site for a length of time until storage space becomes an issue.
- Blocks are routinely retrieved when slides need to be made. Delays in returning these blocks to the archive can cause blocks to be placed in the wrong location, resulting in delays when trying to locate blocks in this situation. Often, the entire archive needs to be searched manually to locate the missing block.
- Blocks are stored off-site after on-site storage capacity is exceeded, using the same numerical storage method.
This storage process works well for small numbers of samples but is quickly overrun when thousands of blocks begin to accumulate. The retrieval and return process can be error-prone, leading to potential specimen loss, delays in retrieval, and excessive time spent re-cataloging and locating blocks, all translating to patient impacting events.