What is tissue microarray and its purpose?

• A. A single, large block for manual sectioning.
• B. A frozen block used for RNA profiling.
• C. A paraffin block containing many tissue cores arrayed in a grid to enable high-throughput histologic analysis.
• D. An imaging modality for in vivo analysis.

Answer: (C)

Tissue microarray is a paraffin block that contains many tissue cores arrayed in a grid, enabling high-throughput histologic analysis. Tiny cores are punched from individual donor tissue blocks and embedded into a single recipient block in a precise grid. Sections cut from this block are stained simultaneously, so you can compare biomarker expression across dozens or hundreds of samples under identical experimental conditions. This saves time, reagents, and allows standardized comparisons across many cases. It’s widely used for screening protein or gene expression patterns by immunohistochemistry or in situ hybridization in translational research. Keep in mind that using small cores can introduce sampling bias if the tumor is heterogeneous, and adequate tissue must be available in the original blocks.