RCL2, a potential formalin substitute for tissue fixation in routine pathological specimens.

Aims: To investigate RCL2 as a fixative for tissue fixation in routine histopathological examination and to assess tissue suitability for ancillary investigations.

Methods And Results:   Forty-nine samples from 36 fresh specimens were cut into three equal pieces and fixed in RCL2 diluted in 100% ethanol, RCL2 in 95% ethanol, or neutral buffered formalin as control. Suitability for microtomy, quality of histomorphology, histochemistry, immunohistochemistry, fluorescent and silver in-situ hybridization analysis and extracted genomic DNA were assessed. Microtomy was straightforward in most tissue blocks, but there was difficulty in cutting in approximately a quarter of samples, which required careful handling by an experienced technician. There were no significant differences in tissue morphology between RCL2- and formalin-fixed tissues (P=0.08). Generally, the quality of histochemical staining, immunohistochemistry and in-situ hybridization were comparable to that of formalin-fixed tissues. Inconsistent immunoreactivity was noted, however, with antibodies against pan-cytokeratin and progesterone receptor. Genomic DNA concentration was higher in RCL2-fixed tissues. Using RCL2 diluted in 95% ethanol did not affect fixation quality.

Conclusion: RCL2 is a potential formalin substitute suitable as a fixative for use in routine histopathological examination; however, difficulty in microtomy and occasional discrepancies in immunohistochemical reactivity require further optimization of the methodology.