Ultrastructural examination is sometimes necessary for diagnosis of surgical pathology material. Not uncommonly, tissue is not fixed in 3% glutaraldehyde prior to realizing that electron microscopy would be valuable or even necessary to render a diagnosis. It is well known that formalin can be an adequate fixative for ultrastructural evaluation of tissue. Increasingly, non-formalin based fixatives have become more popular with routine surgical pathology practice. Prefer™, a glyoxal-based fixative, has become a popular substitute for formalin in many institutions. We are not aware of any study that has compared ultrastructural morphology of tissue fixed in formalin to tissue fixed in a glyoxal-based fixative.

To address this question, we took sections of fresh tissue from three different tumors (metastatic melanoma involving a lymph node, squamous cell carcinoma of the lung, and mixed papillary serous and clear cell carcinoma of the ovary) and fixed a portion of each in 3% glutaraldehyde, 10% neutral buffered formalin, and Prefer™.