New Caledonia (NC), a French territory in the Pacific, has the highest worldwide incidence of thyroid cancer1. We have previously shown a high prevalence of BRAFV600E mutation in this population in association with increased numbers of multifocal bilateral PTC. In this study, we aim to extend this study and to in a subset of BRAFV600E negative patients examine the incidence of other known BRAF mutations. Associations of these mutations with histopathological features were also examined.
The BRAF V600E mutation status was determined in 121 micro-dissected Formalin Fixed Paraffin Embedded (FFPE) PTC tumour tissue obtained from Laboratoire d'Anatomie et Cytopathologie, Nouméa, NC (n=49) and from RPA Hospital, Australia (n=72). BRAF V600E negative NC samples (n=15) were also examined for presence of BRAF V600Ec, V600R, V600D and V600K mutations. Pathological data were obtained from histopathology reports and patients’ medical records. Data was analysed by Chi squared analysis.
In both populations, PTC was more common in females, similar to the pattern worldwide. BRAF V600E prevalence was 64% in NC and 55% in the Australian cohort and this mutation was significantly more common in NC multifocal bilateral tumours (NC: 92% vs Australian: 67%, P<0.005). The further screening for BRAF mutations in BRAFV600E negative samples from NC found that 13% presented BRAF V600Ec and 13% presented BRAF V600R (with no overlap between the two mutations). These incidences are higher than expected (4.3% and 4.9% respectively) for a given population. BRAF V600D and V600K mutations were not detected. The BRAFV600Ec mutation was only found in bilateral PTC and BRAF V600R only in unilateral PTC.
The higher prevalence of the BRAFV600E and BRAFV600Ec mutation in the NC cohort with multifocal bilateral PTC may indicate more aggressive tumours in these individuals. Whether the NC population has increased incidence of other BRAF requires further investigation.