New Caledonia (NC), a French territory in the Pacific, has the highest incidence of thyroid cancer with an age standardized incidence rate of 71.4/100,000 in Melanesian women[1]. To date, the only molecular genetic study in this population was on RET/PTC in papillary thyroid carcinoma (PTC)[2]. The prevalence of BRAF V600E mutation and its association with histopathology features is not known. Therefore, we aim to investigate the BRAF V600E mutation status in NC patients with PTC and compare this to an Australian cohort.
The BRAF V600E mutation status was determined in 87 micro-dissected Formalin Fixed Paraffin Embedded (FFPE) PTC tumour tissue obtained from Laboratoire d'Anatomie et Cytopathologie, Nouméa, New Caledonia(n=30) and from Royal Prince Alfred Hospital, Australia (n=57). Pathological data were obtained from histopathology reports and patients’ medical records. Data was analyzed using Chi squared analysis.
In both populations, PTC was more common in females, similar to the pattern worldwide. 47% of NC PTC were multifocal involving both lobes. BRAF V600E prevalence was 64% in NC and 55% in the Australian cohort. Furthermore, the mutation was significantly more common in NC multifocal bilateral tumours (NC: 88% vs Australian: 67%, P<0.005).
Table 1: Demographic, Histopathology and BRAF V600E Prevalence
|
Variables |
New Caledonia (n=30) |
Australia (n=57) |
|
Female : Male |
22:11 (2:1) |
46:18 (2.5:1) |
|
Multifocal |
47% |
44% |
|
unilateral |
3/14 (21%) |
8/25 (32%) |
|
bilateral |
11/14 (79%) |
17/25 (68%) |
|
BRAF V600E +ve |
N=21 (64%) |
N=35 (55%) |
|
Multifocal |
9/21 (44%) |
13/35 (37%) |
|
unilateral |
1/9 (12%) |
4/13 (33%) |
|
bilateral |
8/9 (88%)* |
9/13 (67%) |
*P<0.005 different from the Australian population
The high prevalence of the BRAF V600E mutation in the NC population suggests its utility as a diagnostic marker of PTC. Further the association of the BRAF V600E mutation in the NC cohort with multifocal bilateral PTC may indicate more aggressive tumours in these individuals.