ABSTRACT
SUMMARY: Fixation is a crucial step in processing of tissue specimen for preservation of cellular architecture and composition of cells. Alcohol-based fixatives are considered some of the most promising alternatives to formalin. We evaluated the performance of alcohol-based fixatives (EthMeth and methacarn) and formalin as a comparator fixative in the research laboratory. Following 24 hours of fixation, tissue morphology and cellular details of the liver, spleen and brain (cerebral cortex) were evaluated. Morphological characteristics were evaluated by gross observations and analyzing cellular details, tissue architecture and overall staining characteristics (Hematoxylin and Eosin). EthMeth and methacarn fixation gave generally comparable and satisfactory results on the tissue morphology and subsequent identification of tissue characteristics. Particularly, tissues were well preserved and all nuclear as well as cytoplasmic details were clearly visible. However, formalin fixed tissues showed some peculiarity such as improper fixation, mild shrinkage, and alterations of tissue components. These results confirm that alcohol-based fixation is the superior alternative to formalin for preservation of tissue morphology. However, it is required to standardize the formalin-free methods and harmonize diagnosis in the laboratory worldwide.
RESUMEN: La fijación es un paso crucial en el procesamiento de muestras de tejido para preservar la arquitectura celular y la composición de las células. Los fijadores a base de alcohol se consideran algunas de las alternativas más prometedoras a la formalina. Evaluamos el rendimiento de los fijadores a base de alcohol (EthMeth y metacarn) y formalina como fijador comparativo en el laboratorio de investigación. Después de 24 horas de fijación, se observó la morfología del tejido y los detalles celulares del hígado, bazo y corteza cerebral. Se evaluaron las características morfológicas mediante observaciones generales y analizando detalles celulares, arquitectura de tejidos y características generales de tinción (hematoxilina y eosina). La fijación de EthMeth y metacarn dio resultados generalmente comparables y satisfactorios en la morfología del tejido y la posterior identificación de las características del mismo. Particularmente, los tejidos estaban bien conservados y todos los detalles nucleares y citoplasmáticos eran claramente visibles. Sin embargo, los tejidos fijados con formalina mostraron cierta peculiaridad, tal como una fijación inadecuada, la contracción leve y alteraciones de los componentes del tejido. Estos resultados confirman que la fijación a base de alcohol es la mejor alternativa a la formalina, para preservar la morfología del tejido. Sin embargo, es necesario estandarizar los métodos sin formalina y armonizar el diagnóstico en los laboratorios.
Subject(s)
Tissue Fixation/methods , Alcohols/chemistry , Fixatives , Formaldehyde/chemistry , Chloroform/chemistry , Acetic Acid/chemistry , Methanol/chemistryABSTRACT
PURPOSE: Telomerase is an RNA-dependent DNA polymerase that synthesizes TTAGGG telomeric DNA onto chromosome ends to compensate for sequence loss during DNA replication. It has been detected in 85~90% of all primary human cancers, implicating that its apparent reactivation in tumors may play a role in the tumorigenic process. The purpose of this study was to evaluate telomerase activity in stomach cancer, and to determine whether methacarn-fixed paraffin-embedded tissues can replace frozen tissue sections for the telomerase (TRAP) assay. MATERIALS AND METHODS: Frozen and corresponding methacarn-fixed paraffin-embedded tissue samples were obtained from 51 patients with gastric adenocarcinoma and analyzed for telomerase activity by using a TRAPeze ELISA kit. RESULTS: Telomerase activity was detected in 37 (73%) frozen samples, and in 13 (25%) methacarn-fixed paraffin blocks. Telomerase activity was well correlated with depth of invasion (p=.037) and tumor differentiation (p=.022). CONCLUSION: These data suggest that reactivated telomerase may play a significant role in the tumorigenesis of gastric cancer and may reflect the malignant potential of the tumor. It is noteworthy that methacarn- fixed tissue cannot as yet substitute for the frozen tissue in the TRAP assay.