Utility of Formalin-Fixed Surgical and Autopsy Specimens for Electron Microscopy

Abstract

One of the limitations in applying electron microscopy to the study of problems in human pathology has been the failure to have available fresh osmium-fixed tissue for the classical technics of preparation. In this study, autopsy, surgical, and biopsy specimens which had been fixed in neutral or neutral-buffered formalin were used for fine structural examination. Electron microscopic preparations of needle biopsies and other small surgical specimens which had been fixed immediately in neutral or neutral-buffered formalin were almost as satisfactory as those from tissue which had been fixed immediately in osmium tetroxide. Tissue which had remained in formalin for periods of time as long as at least 3 months retained fine structure sufficiently well for it to be useful in the study of a wide variety of pathologic processes. Larger surgical specimens that had been placed in formalin immediately after removal yielded very good results, provided the small specimens for electron microscopy were obtained from outer portions of the tissue which had come in direct contact with the fixing fluid. Specimens from surgical or autopsy material which were not placed in formalin until several hours after removal or after death revealed marked alterations in tissue fine structure owing to autolysis. If less than 2 hr had elapsed before fixation, however, the tissue preservation was usually fairly good, except for mitochondrial swelling and clumping of nuclear chromatin granules. Even in tissue fixed 6 to 8 hr after death, certain structural features could be studied electron microscopically, although cytoplasmic fine structure was usually greatly distorted. With certain reservations and limitations in mind, it is believed that formalin-fixed surgical and autopsy specimens may be utilized in the study of many of the problems in human pathology.