Within this context, normal pituitary cells and PitNETs express the neurotrophin receptor tropomyosin receptor kinase A (TrkA) [9,23,24], which exhibits oncogenic alternative TrkAIII splicing in human neuroendocrine neuroblastomas (NBs), Merkel Cell polyomavirus (MCPyV) positive Merkel cell carcinomas, cutaneous malignant melanomas, and acute myeloid leukemia [25,26,27,28,29]. This evidence concerns the gene NTRK1 and Nijmegen breakage syndrome.