Over-represented in this last group are a cluster of tumours (S1) described by Gadd and colleagues that do not harbour mutations in WT1, CTNNB1 or AMER1. These tumours usually show retention of imprinting at IGF2, have a distinct gene expression pattern and have highly differentiated monomorphic epithelial histology [30, 31]. Here, IGF2 is linked to neoplasm.