GNAS Mutations in Fibrous Dysplasia: A Comparative Study of Standard Sequencing and Locked Nucleic Acid PCR Sequencing on Decalcified and Non-Decalcified Formalin Fixed Paraffin Embedded Tissues

摘要

It is well-known that fibrous dysplasia is characterized by the presence of activating mutations involving G-nucleotide binding protein alpha sub unit (GNAS) involving codon R201 and rarely codon 227 with a mutation frequency between 45–93%. Herein, we investigate the sensitivity of detection of GNAS mutations in exons 8 and 9 using standard and a high sensitive locked nucleic acid PCR (LNA-PCR) sequencing in 52 cases of fibrous dysplasia. In view of the recent report of GNAS mutations in a small number of low grade osteosarcomas, we also tested in addition 12 cases of low grade osteosarcomas. GNAS exon 8 mutations p.R201H (31%), p.R201C (15%) and p.R201S (2%) were identified in 48% of fibrous dysplasia cases. LNA-PCR/sequencing identified only one codon 201 positive case within the mutation negative cases tested by standard PCR and Sanger sequencing. No mutations were identified in any of the low grade osteosarcomas by standard and LNA-PCR/sequencing. There was no association between age, site, size, specimen type and mutational status. No exon 9 or codon 227 mutations were identified in any of tested cases. There was a significant difference in the sensitivity of the assay between decalcified and non decalcified FDs (31 vs. 70%, p=0.002). LNA-PCR has no added value in enhancing detection sensitivity for GNAS mutations in fibrous dysplasia. In addition to decalcification, innate somatic mosaicism contributes to the decreased sensitivity in mutation detection.