title: Assessment of morphology, antigenicity, and nucleic acid integrity for diagnostic thyroid pathology using formalin substitute fixatives.
abstract: 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.
authors.affiliation: Inserm ERI-21, Faculty of Medicine, University of Nice Sophia Antipolis, 06107 Nice, France.
authors.forename: Sandra
authors.initials: S
authors.lastname: Lassalle
authors.forename: Véronique
authors.initials: V
authors.lastname: Hofman
authors.forename: Ilie
authors.initials: I
authors.lastname: Marius
authors.forename: Virginie
authors.initials: V
authors.lastname: Gavric-Tanga
authors.forename: Patrick
authors.initials: P
authors.lastname: Brest
authors.forename: Katia
authors.initials: K
authors.lastname: Havet
authors.forename: Catherine
authors.initials: C
authors.lastname: Butori
authors.forename: Eric
authors.initials: E
authors.lastname: Selva
authors.forename: José
authors.initials: J
authors.lastname: Santini
authors.forename: Baharia
authors.initials: B
authors.lastname: Mograbi
authors.forename: Paul
authors.initials: P
authors.lastname: Hofman
mesh_terms: D005404:Fixatives; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods*; D009696:Nucleic Acids / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods*; D013961:Thyroid Gland / Q000378:metabolism / Q000473:pathology; D013964:Thyroid Neoplasms / Q000378:metabolism / Q000473:pathology; D016707:Tissue Fixation / Q000379:methods*
chemical_list: D005404:Fixatives; D009696:Nucleic Acids