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Updated: Jun 19, 2026
An Ex vivo Culture System to Study Thyroid Development
Published on: June 6, 2014
Assessment of morphology, antigenicity, and nucleic acid integrity for diagnostic thyroid pathology using formalin
Sandra Lassalle1, Véronique Hofman, Ilie Marius
1Inserm ERI-21, Faculty of Medicine, University of Nice Sophia Antipolis, 06107 Nice, France.
Insights
Formalin substitute fixatives offer good morphology for thyroid tissues. FineFIX and RCL2 excel in preserving antigenicity and nucleic acid integrity for molecular analysis.
Area of Science:
- Pathology
- Histology
- Molecular Biology
Background:
- Formalin fixation is standard in surgical pathology but is being re-evaluated due to new diagnostic methods and regulations.
- Assessing formalin substitutes requires evaluating morphology, antigenicity, and nucleic acid integrity.
- Thyroid pathologies present a diverse range of tissues for fixative comparison.
Purpose of the Study:
- To compare formalin substitute fixatives against formalin and cryoconservation for thyroid tissues.
- To assess the impact of different fixatives on morphology, antigenicity, and nucleic acid quality.
- To identify optimal fixatives for various diagnostic and molecular procedures in thyroid pathology.
Main Methods:
- Specimens from various thyroid pathologies were fixed using formalin and four substitutes (Glyo-Fixx, FineFIX, ExcellPlus, RCL2) under different conditions.
- Tissues underwent standard staining and immunohistochemistry with a panel of antibodies.
- DNA, RNA, and microRNA integrity were analyzed from deparaffinized sections and compared to cryosections.
Main Results:
- Histomorphology and staining were well-preserved across all tested fixatives.
- Formalin, FineFIX, and RCL2 demonstrated superior performance in immunohistochemistry.
- FineFIX and RCL2 yielded the highest quantity and quality of nucleic acids (DNA, RNA, microRNA).
Conclusions:
- Formalin substitute fixatives provide adequate histomorphologic quality for stained thyroid tissues.
- Specific substitutes, namely FineFIX and RCL2, show promise for enhanced immunohistochemical and molecular analyses in thyroid pathology.
- The choice of fixative can be optimized based on the specific diagnostic or molecular requirements for different thyroid pathologies.
Background:
With the advent of the formaldehyde standard law in France, and because of the impact of new methods for diagnosis and prognosis in pathology, formalin replacement in surgical pathology laboratories is currently being discussed in France. However, a set of criteria must be assessed before introducing a formalin substitute fixative. The objective of this study was to compare formalin substitute fixation with formalin fixation and cryoconservation of tissues from several benign and malignant thyroid pathologies with respect to morphology, antigenicity, and nucleic acid (RNA, DNA, microRNA) integrity.
Methods:
Calibrated specimens (200 mg, 1 cm(2) each) from four conventional papillary thyroid carcinomas, four follicular variant of papillary thyroid carcinomas, three minimally invasive follicular carcinomas, four thyroid adenomas, five thyroid nodular hyperplasias, and five normal thyroid tissues were fixed for 6, 12, or 24 hours, in different fixatives (formalin, Glyo-Fixx, FineFIX, ExcellPlus, RCL2) at room temperature or at 4 degrees C. Tissues were stained (hematoxylin-eosin, periodic acid Schiff, trichromic Masson, and Sweet-Gordon staining) and their antigenicity determined by immunohistochemistry (performed with HBME-1, galectin-3, CK19, vimentin, CD31, and KL1 antibodies). Evaluation by four pathologists was made blinded. The quantity and quality of DNA, RNA, and two representative microRNA extracted from deparaffinized sections of paraffin embedded specimen were compared with that of cryosections.
Results:
The staining and morphology were not altered by the use of different fixatives. However, formalin, FineFIX, and RCL2 gave the best results for immunohistochemistry. Moreover, FineFIX and RCL2 gave the highest amount of nucleic acids and of the best quality.
Conclusions:
All the formalin substitute fixatives used in this study provided good histomorphologic quality for the different stained thyroid tissues, but individually, some fixatives performed better for immunohistochemical and molecular biological procedures for different thyroid pathologies.
