Patients with an ectopic humoral syndrome frequently have neoplasms at the advanced stage, for which curable surgery is impossible, with the exception of cases of classical neuroendocrine tumours. Demonstration of the neuroendocrine characteristics of neoplastic cells is useful for the definite diagnosis in many cases of ectopic hormone syndromes. Several neuroendocrine features of neoplastic cells are described in Fig. 21.9.
