Research article

Preservation of biomolecules in breast cancer tissue by a formalin-free histology system

Mehdi Nassiri¹ , Sharon Ramos¹ , Hajir Zohourian¹ , Vladimir Vincek² , Azorides R Morales¹ and Mehrdad Nadji¹

¹Department of Pathology, University of Miami Miller School of Medicine, Miami, Florida, USA

²Department of Pathology, University of Florida, Gainesville, Florida, USA

author email corresponding author email

BMC Clinical Pathology 2008, 8:1doi:10.1186/1472-6890-8-1

Published:	29 January 2008

Abstract

Background

The potential problems associated with the use of formalin in histology, such as health hazards, degradation of RNA and cross-linking of proteins are well recognized. We describe the utilization of a formalin-free fixation and processing system for tissue detection of two important biopredictors in breast cancer – estrogen receptor and HER2 – at the RNA and protein levels.

Methods

Parallel sections of 62 cases of breast cancer were fixed in an alcohol-based molecular fixative and in formalin. Molecular fixative samples were processed by a novel formalin-free microwave-assisted processing system that preserves DNA, RNA and proteins. Formalin-fixed samples were processed using the conventional method. Estrogen receptor was assessed by immunohistochemistry and real-time PCR. HER2 was assessed by immunohistochemistry, FISH, CISH and real-time PCR.

Results

The immunohistochemical reaction for estrogen receptor was similar in molecular- and formalin-fixed samples (Spearman Rank R = 0.83, p < 0.05). Also HER2 result was similar to that of formalin-fixed counterparts after elimination of antigen retrieval step (Spearman Rank R = 0.84, p < 0.05). The result of HER2 amplification by FISH and CISH was identical in the molecular fixative and formalin-fixed samples; although a shorter digestion step was required when using the former fixative. Real-time PCR for both estrogen receptor and HER2 were successful in all of the molecular fixative specimens.

Conclusion

The formalin-free tissue fixation and processing system is a practical platform for evaluation of biomolecular markers in breast cancer and it allows reliable DNA and RNA and protein studies.