Histomorphologic Assessment of Formalin Substitute Fixatives for Diagnostic Surgical Pathology

Context: In 1987, the Formaldehyde Standard became law in the United States, alerting laboratory workers to the potential carcinogenicity of formaldehyde. As a result, a variety of proprietary fixatives were developed for use in surgical pathology.

Objective: To assess histomorphology with different formalin substitute fixatives.

Design: Four experienced board-certified surgical pathologists examined 7 specimens (hepatocellular carcinoma, ovarian sex cord/stromal tumor, myxoid liposarcoma, uterine endometrioid adenocarcinoma, splenic follicular hyperplasia, infiltrating mammary carcinoma, and cecal signet ring carcinoma) fixed with formalin and 5 proprietary fixatives advertised as formalin replacements. In a blind study, the pathologists rated cellular outlines, cytoplasmic detail, nuclear detail, erythrocyte integrity, lymphocyte integrity, overall morphology, and overall staining in each case.

Results: Formalin received the highest overall morphology and staining scores, followed by Glyo-Fixx, STF-Streck, Omnifix, Histochoice, and Histofix. Formalin also received the highest scores in cellular outline and erythrocyte integrity. Individually, some fixatives performed better in different areas than others. Glyo-Fixx performed as well as formalin for overall morphology and provided highest nuclear detail and lymphocyte appearance scores. Omnifix II gave best results for cytoplasmic detail.

Conclusion: In this blind study, formalin fixation provided the highest histomorphologic quality for tissue stained with hematoxylin-eosin and examined for diagnostic surgical pathology. Should the use of formalin be discontinued, pathologists will have to familiarize themselves with a different set of microscopic details associated with the replacement fixatives.