Carnoy's solution is an adequate tissue fixative for routine surgical pathology, preserving cell morphology and molecular integrity

Abstract

Aims: To compare Carnoy's solution (CS) and 10% neutral buffered formalin solution (NBF) as tissue fixatives in colorectal cancer specimens.

Methods and results: Surgical specimens from patients with colorectal cancer were analysed. Three groups were studied, as follows: group 1 consisted of 16 paired samples fixed in CS and NBF; and groups 2 and 3 consisted of 14 prospective and 80 retrospective samples, respectively, both randomized for fixation in CS or NBF. Groups 1 and 2 were analysed for amount, quality and integrity of DNA. Morphological analysis, including some of the usual special stains and polymerase chain reaction (PCR), were also performed for group 1, and Sanger sequencing for group 2. Immunohistochemical (IHC) reactions for mismatch repair proteins were studied in groups 1 and 3. Fixative performances were similar for morphology, special stains, and IHC reactions, as well as for the amount, quality and integrity of extracted DNA. PCR amplification was not possible in two cases from CS group 1. Sanger sequencing gave conclusive results for the CS samples tested.

Conclusions: Carnoy's solution and NBF are equivalent fixatives for colorectal cancer specimens and are adequate for routine utilization in surgical and molecular pathology.

Keywords: Carnoy's solution; DNA extraction; formalin; immunohistochemistry; tissue fixation.