Tissue Heterogeneity as a Pre-analytical Source of Variability

A low level of reproducibility is the shortcoming of clinical studies where human tissues are used, especially in oncology (EGAAP, Evaluation of Genomic Applications and Prevention Working Group (2013) Recommendations from the EGAPP Working Group: can testing of tumor tissue for mutations in EGFR pathway downstream effector genes in patients with metastatic colorectal cancer improve health outcomes by guiding decisions regarding anti-EGFR therapy? Genet Med: Off J Am Coll Med Genet 15:517–527, Simon RM, Paik S, Hayes DF (2009) Use of archived specimens in evaluation of prognostic and predictive biomarkers. J Natl Cancer Inst 101:1446–1452). This could be due to the high variability of the pre-analytical conditions of tissue managing and preservation, but also to other two causes. One is the low level of standardization of the methods that is pertinent to the analytical phase. Heterogeneity of tissues is the other problem and it can be considered to be actually related to pre-analytical procedures. Indeed, it is a pre-condition that has to be taken into consideration before the specific analysis. Not all the consequences of heterogeneity can be more or less easily avoided by carefully choosing the tissues to be analyzed.