Histomorphologic assessment of formalin substitute fixatives for diagnostic surgical pathology

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.

To assess histomorphology with different formalin substitute fixatives.

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.

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.

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.