1. Research Techniques Made Simple: Tissue Microarray Kathleen Barrette 1, Joost J. van den Oord 2, Marjan Garmyn 1 1. Laboratory of Dermatology, Department of Oncology, KU Leuven, Leuven, Belgium 2. Translational Cell & Tissue Research, Department of Imaging and Pathology, KU Leuven, Leuven, Belgium

2. History of TMA 1986: first description of TMA Wan WH, Fortuna MB, Furmanski P: A rapid and efficient method for testing immunohistochemical reactivity of monoclonal antibodies against multiple tissue samples simultaneously. J Immunol Methods 103:121-129 (1987). 1998: first development of a device which could rapidly and reproducibly produce TMAs Kononen J, Bubendorf L, Kallioniemi A, Barlund M, Schraml P, Leighton S, Torhorst J, Mihatsch MJ, Sauter G, Kallioniemi OP: Tissue microarrays for high-throughput molecular profiling of tumor specimens. Nat Med 4:844-847 (1998).

3. TMA construction 1.Delineate area of interest - Paraffin block cut on a microtome -Stained with hematoxylin & eosin -Area of interest is delineated

4. TMA construction 2.The cylindrical core -Needle is placed above area of interest -Punch out the core by moving the needle down and up into the original donor block -Tissue core is situated in the hollow needle

5. TMA construction 3.The recipient block -Core is placed in an empty, predrilled recipient block -Down movement of needle and upper part of the needle to push out the core

6. TMA construction 4.The new TMA glass slide -Recipient block is heated to 37°C to fix cores -Block is cut on a microtome and mounted on a glass slide -Slides can be stained with hematoxylin & eosin, immunohistochemistry or other applications

7. Applications of a TMA To screen tissue samples from a large patient cohort – for the expression of a specific protein, via immunohistochemistry – for the presence or absence of a specific gene sequence via fluorescence in situ hybridization (FISH)

8. Advantages of TMA Simultaneous analysis of a large number of specimens – Multiple cores from multiple donor blocks Construction of in vivo tumor progression model – Easy to include different tumor progression stadia Experimental uniformity – Each tissue core is treated in an identical manner (same antigen retrieval, temperature, incubation time, washing procedure, and reagent concentration) Decreased volume, time, and cost

9. Limitations of TMA Less suited for heterogeneous tissues – Just one core was selected from whole paraffin block – Take multiple cores from one block if tissue is heterogeneous Expensive – Commercial TMA builder is expensive – Constructing a TMA without a commercial TMA builder is possible but time-consuming Variations in antigenicity – Variations in antigenicity of stored archival samples