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Short answer: A tissue microarray (TMA) is a single paraffin block that holds many small tissue cores taken from different source blocks, so one slide can be stained and scored for a biomarker across many cases. It trades the area of each sample for throughput. This page is general laboratory-method information, not medical advice.
Definition and scope
A tissue microarray is built by extracting small cylindrical cores from standard formalin-fixed, paraffin-embedded (FFPE) tissue and re-embedding them in a grid inside a new recipient block. The tissue microarray was first described by Kononen in 1998 (Voduc, Kenney and Nielsen, Semin Radiat Oncol 2008). Once the recipient block is cut, each section carries every core, so a single staining run covers all cases on the block.
Searchers use several names for the same thing. “Tissue microarray block” means the finished recipient block; “micro tissue array” is a reordering of the same term. Neither should be confused with a DNA microarray, which measures nucleic acids on a chip rather than arranging tissue cores on a slide.
Donor block, recipient block and TMA block
- Donor (source) block: the original FFPE block from one case.
- Recipient block: the blank paraffin block that receives the cores. Once filled it is the TMA block.
- Sector map: the record of which case sits at which grid position, used to place cores and to score them later.
How a tissue microarray is used in practice
In the construction workflow described by Voduc et al., a pathologist marks a representative area on a haematoxylin and eosin (H&E) section of each donor block. An arrayer then punches a core from the blank recipient block and a second needle takes the matching core from the donor block into that hole, following the sector map.
The main applications named in the same review are validating immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) biomarkers in large cohorts, using archival tissue that can be linked to outcome data, and comparing results between laboratories. Staining a few TMA sections instead of many whole sections also saves reagents and technician time. For slide handling in general, see what a microscope slide is; for tissue-level spatial methods that work differently, see spatial proteomics and tissue mapping.
Manual vs automated construction
The National Society for Histotechnology compares the two approaches as follows.
| Aspect | Manual | Automated |
|---|---|---|
| How cores are placed | Silicone mold, biopsy punch and plunger; block is incubated in an oven to adhere the cores | Instrument (for example the TMA Grand Master from 3DHISTECH) drills recipient holes and punches donor cores |
| Cost | Low; molds are reusable | Main drawback is instrument cost |
| Speed and error | Slower, more human error | Less error and core breakage |
| Failure points | Cores can break, wax can crack, blocks can melt if overheated, uneven core height gives inconsistent sectioning | Fragile tissue can still break; if the H&E annotation is misaligned with the block image, the wrong area is punched |
Core number and loss: a planning checklist
The figures below come from the Voduc et al. review and are the basis for the checklist that follows.
- Core diameter: 0.6 mm to 2.0 mm are used, 0.6 mm most often. At 0.6 mm, at least 400 cores fit in a standard-sized recipient block.
- Cores per case: most validation studies showing good concordance with whole sections used one to four cores per source block.
- Reported loss: one TMA was associated with 25-30% uninterpretable cores; combined analysis of three TMAs reduced data loss to 5-7%.
- Decide the cores per case before building, within the one-to-four range used in validation studies.
- Choose the core diameter against the grid capacity you need (0.6 mm gives the highest capacity of the sizes in use).
- Plan for lost cores: sectioning, transfer and staining all cause loss, and the review reports that combining three TMAs cut data loss sharply.
- Keep the sector map with the block and confirm that the marked H&E area matches what is punched.
- Plan one marker per analysis: each biomarker must be assessed separately.
Common misunderstandings
- “A core represents the whole tumour.” The most frequent criticism of TMAs is the small size of each core, so heterogeneity is a real limit. The same review notes that whole sections also sample only a small part of a tumour.
- “A TMA is a discovery tool.” It is better suited to validating a candidate marker than to screening many markers at once.
- “Automation removes error.” It reduces it, but misaligned annotation can still send the punch to the wrong area.
FAQ
What is a tissue microarray?
A paraffin block holding many small cores from different source blocks, so one slide can be stained for a marker across many cases.
What is a tissue microarray block?
The recipient paraffin block after it has been filled with cores arranged on a grid.
What is a micro tissue array?
It is another phrasing of tissue microarray. The standard term in the literature is tissue microarray (TMA).
How many cores fit in one block?
At 0.6 mm core diameter, at least 400 cores fit in a standard-sized recipient block (Voduc et al., 2008).
Sources
- Voduc D, Kenney C, Nielsen TO. Tissue microarrays in clinical oncology. Semin Radiat Oncol 2008;18(2):89-97. pmc.ncbi.nlm.nih.gov/articles/PMC2292098 (read 2026-11-08).
- National Society for Histotechnology. Creating tissue microarrays: manual vs automated. nsh.org blog, 30 March 2023 (read 2026-11-08).
