Fixation for the 1990's: a review of needs and accomplishments.

Neutral buffered formalin (NBF) has been the standard fixative in histopathology for many decades; however, new technologies and increasing time constraints have made this common fixative less widely applicable. The attributes of universal and ideal fixatives are reviewed and compared with those of NBF. On the strength of a growing body of literature and experience in the histopathology field, zinc formalin solutions are recommended as a functional replacement for NBF. Zinc formalin permits better morphological preservation and preserves immunoreactivity even after prolonged fixation times. Coordinated zinc ions are postulated to maintain macromolecules in their original three-dimensional conformation as formaldehyde forms addition products with them. Significant crosslinking and gross distortion of tertiary structure are thereby avoided.