BRAF and neoplasm: Similarly, although all studies associate the presence of a BRAF V600E mutation with papillary architecture, several studies have reported a higher prevalence of BRAF mutations in tumours classified as tall cell or columnar cell variants of PTC that are associated with more aggressive clinical behaviour and loss of responsiveness to radioiodine (Nikiforova et al, 2003; Begum et al, 2004).