This Technical Specification recommends the handling, documentation and processing of frozen tissue specimens intended for the analysis of extracted proteins during the preanalytical phase before a molecular assay is performed. This Technical Specification is applicable to molecular in vitro diagnostic examinations (e.g., in vitro diagnostic laboratories, laboratory customers, in vitro diagnostics developers and manufacturers, institutions and commercial organisations performing biomedical research, biobanks, and regulatory authorities). Protein profiles and protein-protein interactions in tissues can change drastically before and after collection (due to e.g., gene induction, gene down regulation, protein degradation). Protein species amounts can change differently in different donors’ / patients’ tissues. The expression of genes can be influenced by the given treatment or intervention (surgery, biopsy), or drugs administered for anaesthesia or even treatment of concomitant disease as well as by the different environment conditions after the tissue removal from the body. Therefore, it is essential to take special measures to minimize the described profile changes and modifications within the tissue for subsequent protein analysis. Tissues that have undergone chemical stabilization pre-treatment before freezing are not covered in this document. In addition this document is not applicable for protein analysis by immunohistochemistry.