POMC and neoplasm: Furthermore, based from our case it can be hypothesized that the tumor with hormone secretion required more precursor uptake than the inactive one, possibly through upregulated membrane transport systems: this would explain why the ACTH-secreting tumor and its adjacent lymph-node metastases were accurately identified with F-DOPA-PET, whereas the neighboring nonsecreting NET remained silent, despite the fact that both tumors had similarly low mitotic indexes.