PTPRK and thyroid cancer: Amongst others, mutations in the tumor suppression genes DPC4 [15], AIM1 (‘absent in melanoma1’) and PTPRK (receptor type protein-tyrosine phophastase kappa) [14] are shown in metastatic VIPomas while mutations of the proto oncogene BRAF known to play an important role in thyroid cancer and melanoma were not found [15,18].