Prolonged storage of fixative for electron microscopy: effects on tissue preservation for diagnostic specimens

Prolonged storage of Karnovsky's fixative, at both 4 and -20 degrees C, is possible in the diagnostic electron microscopy setting. Ultrastructural detail was not compromised in specimens processed in fixative that had been stored for 6 months. Evidence of smooth muscle and neuroendocrine differentiation was present in the form of actin filaments/dense bodies and neurosecretory granules, respectively. No difference in preservation was detected between specimens fixed in freshly prepared Karnovsky's fixative and fixative that had been stored at either 4 or -20 degrees C for up to 6 months. Thus, community hospitals can be provided with Karnovsky's fixative on a semiannual basis for surgical pathology specimens that may require electron microscopy for diagnosis.