Both the RET-related survival (presence of RET ligand) and apoptosis (lack of RET ligand) pathways are conserved in sporadic somatotroph tumours [31] and recent results demonstrated that i) overexpression of GDNF is a hallmark of somatotroph tumours, and ii) lower level ARF expression is a prognostic marker for resistance to therapy [30]. Here, CDKN2A is linked to neoplasm.