Methacarn and RCL2, a new noncrosslinking
fixative, were compared to
formalin-fixed or frozen tissue samples of the same invasive
breast carcinoma and were evaluated for their effects on tissue morphology and immunohistochemistry as well as
DNA and
RNA integrity. The histomorphology of
methacarn- or RCL2-fixed
paraffin-embedded
tumors was similar to that observed with the matched
formalin-fixed tissues. Immunohistochemistry using various
antibodies showed comparable results with either
fixative, leading to accurate
breast tumor diagnosis and determination of
estrogen and
progesterone receptors, and HER2 status.
Methacarn and RCL2 fixation preserved
DNA integrity as demonstrated by successful amplification and sequencing of large
DNA amplicons. Similarly, high-quality
RNA could be extracted from
methacarn- or RCL2-fixed
paraffin-embedded MCF-7 cells, whole
breast tumor tissues, or microdissected
breast tumor cells, as assessed by electropherogram profiles and real-time
reverse transcriptase-polymerase chain reaction quantification of various genes. Moreover, tissue morphology and
RNA integrity were preserved after 8 months of storage. Altogether, these results indicate that
methacarn, as previously shown, and RCL2, a promising new
fixative, have great potential for performing both morphological and molecular analyses on the same fixed tissue sample, even after
laser-capture microdissection, and can open new doors for investigating small target lesions such as premalignant breast lesions.