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Nucleic Acid Quality Preservation by an Alcohol-based Fixative: Comparison With Frozen Tumors in a Routine Pathology Setting

Hostein, Isabelle PhD; Stock, Nathalie MD; Soubeyran, Isabelle MD; Marty, Marion MD; De Mascarel, Isabelle MD; Bui, Mathieu MD; Geneste, Gaëlle MedTech; Petersen, Marie-Claude MedTech; Coindre, Jean-Michel MD; MacGrogan, Gaëtan MD

Diagnostic Molecular Pathology: March 2011 - Volume 20 - Issue 1 - p 52–62
doi: 10.1097/PDM.0b013e3181e71ba5
Original Articles
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Pathologic diagnosis requires tissue fixation for histologic and immunohistologic analysis, and formalin is routinely used for this. The disadvantage of this fixative is its inability to preserve nucleic acids. Pathologic tumor diagnosis requires extensive molecular analyses, for which formalin fixation may be not adequate. Recently, an alcohol-based fixative (molecular fixative, MF) was described that allows nucleic acid preservation as well as histologic and immunohistologic studies. Moreover, the MF fixation processing system (Xpress) is fast and is well adapted to a routine process. We evaluated RNA and DNA quality within 1 month and after 1 year for 10 breast carcinomas and 20 sarcomas fixed in MF in comparison with the corresponding frozen tumors. The quality of DNA extracted from the MF-fixed tissue was similar to that extracted from the frozen tumors. The quality of RNA extracted from the MF-fixed tissue was lower than that of frozen tumors; nevertheless, a majority of RNA integrity number (RIN) values were greater than 7. Gene expression quantification by real-time polymerase chain reaction gave comparable results between tumors fixed with MF and frozen tumors. Tissue fixation at 4°C with the MF improved the RNA quality measured by the RIN value. However, after storage for 1 year at room temperature, although DNA quality was preserved, RNA extracted from tissues fixed with the MF was degraded. Tissue fixation with the MF is an important improvement for molecular pathologic diagnosis, enabling a combination of routine pathologic diagnoses and current molecular diagnoses if they are carried out near the processing time.

Department of Pathology, Institut Bergonié, Bordeaux, France

Reprints: Isabelle Hostein, PhD, Department of Pathology, Institut Bergonié, 229 cours de l'Argonne, 33076 Bordeaux cedex, France (e-mail: hostein@bergonie.org).

Supported by the French National Institute of Cancer (INCA), which provided a grant entitled « Axe soutien en faveur des tumorothéques ou laboratoires associés pour l'évaluation des nouvelles techniques de préservation des échantillons tumoraux ».

There is no conflict of interest declared.

© 2011 by Lippincott Williams & Wilkins.