Immunological Features of Neuroendocrine Neoplasms and Adrenal Tumors

Neuroendocrine neoplasms, which occur throughout the human body, as well as adrenocortical carcinoma and pheochromocytoma, which originate in the adrenal gland, are primarily classified as rare malignancies. Immunotherapy, including immune checkpoint inhibitors (ICIs), is generally not incorporated into the standard care protocols for these tumors. The clinical efficacy of ICIs in these tumors has been modest. This may be due to the biological heterogeneity of these tumors. The tumor immune microenvironment profiles are heterogeneous among the molecular subtypes of pheochromocytoma/paraganglioma, suggesting a potential benefit observed in selected subgroups. Poorly differentiated neuroendocrine carcinoma (NEC) exhibits spontaneous activation of adaptive immunity, unlike well-differentiated neuroendocrine tumors. A delta-like ligand 3-directed T-cell-engaging bispecific antibody, tarlatamab, has recently demonstrated prolonged survival in small cell lung cancer, and investigations into its use in extrapulmonary NEC are underway. This review examines the immunological features of representative neuroendocrine and adrenal tumors (neuroendocrine tumor, neuroendocrine carcinoma, adrenocortical carcinoma, and pheochromocytoma/paraganglioma). In the future, elucidating the relationship between specific molecular subtypes and immunophenotypes may facilitate the development of personalized therapies and guide clinical investigations in promising patient subpopulations.