Tissue and Cell Molecular Analysis (TACMA) Tissue Handling

The Mayo Tissue Registry includes paraffin-embedded tissue from as early as 1905. Many of the older blocks are too brittle to section due to the poor quality of the wax or paraffin. The tissues from these older blocks can be salvaged with good results for histology and immunohistochemistry by re-embedding in new paraffin. The ability to salvage these older tissues greatly expands Mayo’s tissue resource.

Also, some frozen samples, such as biopsies and small xenograph tissues, are too small and thin to be handled and sectioned properly without the use of mounting media. In these instances, such tissues can be placed in base molds and snap frozen in OCT, another tissue-embedding media.

TACMA also has the capability of snap freezing fresh tissues using a Histobath cryobath. Use of the Histobath both speeds the process of freezing samples and greatly eliminates “ice artifacts” within the newly frozen tissues. Such freezing can be done either with or without OCT, at the investigator’s request.

Occasionally, in the case of heterogeneous frozen tissue blocks, researchers request “enrichment.” Essentially, this entails one or more of the TACMA personnel physically dissecting previously frozen samples under properly cold conditions. Using hematoxylin and eosin stains marked by a pathologist for reference, this procedure can greatly improve the percentage of either tumor or benign tissue in the remaining frozen samples. Alternatively, TACMA will dissect chunks of frozen tissue for use in RNA, DNA, or protein extraction.