We and others have already shown that tumours with a major solid component are more often positive for a RET-PTC 3 arrangement, while tumours that are dominated by a well-differentiated papillary component more often show a RET-PTC 1 rearrangement (Nikiforov et al, 1997; Thomas et al, 1999; Rabes et al, 2000). The gene discussed is RET; the disease is neoplasm.