Neuroendocrine Neoplasms

Neuroendocrine neoplasms are classified as well-differentiated neuroendocrine tumors (NETs) and slow progression neuroendocrine carcinomas (NEC). Well-differentiated NETs exhibit relatively indolent behavior. Slow progression NECs may exhibit highly aggressive behavior, with a rapid metastatic spread that is clinically indistinguishable from pancreatic adenocarcinoma or small cell lung cancer. The Ki-67 proliferative index rate is used to subclassify well-differentiated NETs into low, intermediate, and high-grade, while NECs are by default high-grade and poorly differentiated and divided into small- and large-cell NEC.

NETs of unknown primary origin may derive from the small bowel, pancreas, appendix, colon, rectum, or ovary.[23,24] Somatostatin receptor PET-CT scans are highly effective at identifying primary sites and metastatic sites for well-differentiated NETs, while fluorine F 18-fludeoxyglucose–PET is more appropriate for NEC.[25-27]

For more information, see Gastrointestinal Neuroendocrine Tumors Treatment.

Merkel cell carcinoma is a rare, aggressive, cutaneous malignancy of neuroendocrine origin, usually with primary lesions in the head and neck or in the extremities. However, it may present in the lymph nodes only, with no evident primary site.[28]

For more information, see Merkel Cell Carcinoma Treatment.