The non-crosslinking fixative RCL2®-CS100 is compatible with both pathology diagnosis and molecular analyses

Abstract

Formalin is the key agent for tissue fixation and pathological diagnosis. However, it poorly preserves nucleic acids and this can impair molecular studies. An alternative to formalin would be a fixative which can allow both morphologic and molecular analyses. To assess the suitability of such a fixative, breast (n = 11) and colon (n = 12) tumor samples were fixed in the non cross-linking RCL2®-CS100 fixative and compared to paired formalin-fixed and to frozen samples, the current standards for histology and molecular analyses, respectively. Sections from RCL2®-CS100-fixed samples showed good preservation of cellular and architectural morphology, suitable for routine diagnosis. Although some antibodies required change in the immunohistochemical procedures, quality of the immunohistochemical staining was comparable to that obtained after formalin fixation. HER2 chromogenic in situ hybridization was also successfully performed. High quality DNA could be isolated from RCL2®-CS100-fixed cancer tissues as evidenced by successful amplification of large DNA fragment, CGH array, KRAS and microsatellites genotyping. The quality of RNA from RCL2®-CS100-fixed samples was slightly decreased in comparison to that of RNA isolated from frozen samples, as evidenced by a decreased RNA integrity number but remained exploitable for molecular assays. Our results support the use of the RCL2®-CS100 fixative for histological diagnosis and recovery of high-quality nucleic acids for molecular applications. However, specific procedures for tissue handing and processing, essential to provide high-quality specimens, could limit its use to small target lesions which cannot be frozen without impairing their pathological evaluation.