Tissue microarrays (TMAs) contain multiple tissue cores obtained from formalin fixed paraffin embedded (FFPE) blocks which are punched from a defined area on the tissue. This allows one blank recipient block to contain 1–77 cores from various tissues depending on core size and spread. TMAs are an effective way to perform tests such as immunohistochemistry with various stains and analyses, due to the number of patient samples on one slide (1) with reduced cost of reagents and analysis time.
The development of TMAs for research in cancer are becoming increasingly prevalent, as their use allows researchers to rapidly analyse tumours within tissues and score them at a high and standardised rate for large cohorts making the process faster and cheaper (1). They are also common in diagnostics when used as controls for testing in pathology labs (2). One TMA including breast cancer samples showing various receptor positivity can be put onto one slide and ran as a control for estrogen receptor (ER), progesterone receptor (PR) or human epidermal growth factor receptor 2 (HER2) immunohistochemistry, removing the need for sourcing multiple patient samples.
One limitation is the restricted view of cell morphology in the TMA, as only one core is taken from a specific site within the chosen tumour limiting the overall view of the tumour spread and infiltration in other areas of interest. For cancers which cause small satellite deposits of tumour throughout the specimen, taking one core from an area would not give the scope of the spread and infiltration within the sample. This could lead to skewed data resulting in variations in analysis (3). Another limitation, is the integrity of the residual sample once the core has been extracted. After core extraction, the donor sample block for the TMA is left with a hole in the tissue which compromises the structure and usability for non-TMA projects in the future. Due to the hole in the tissue, this may cause the tissue to “crumble” under pressure and also damage the surrounding tumour deposits. When sectioning a used donor block, the hole may cause the section to break apart making sectioning very difficult, limiting the use of the tissue (4). As an increasingly sought-after way for sample analysis, these points need to be considered when it comes to TMA development to provide efficient high-quality results and preserve tissue.