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September 2014

Neuroendocrine Tumors of Unknown Primary: Is the Primary Site Really Not Known?

Author Affiliations
  • 1Division of Hematology/Oncology, Department of Medicine, University of California, San Francisco
  • 2Division of Surgical Oncology, Department of Surgery, University of California, San Francisco
  • 3UCSF Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco
JAMA Surg. 2014;149(9):889-890. doi:10.1001/jamasurg.2014.216

In approximately 13% of patients who are diagnosed as having neuroendocrine tumors (NETs), the primary site is not known.1 Commonly, biopsy of a liver mass reveals an NET metastasis; in other instances, a lymph node metastasis is found on biopsy of a mesenteric, retroperitoneal, or peripancreatic mass. However, a primary tumor remains elusive. The topic of NETs of unknown primary site perplexes even those experienced in NETs because it raises 5 key questions, each of which we attempt to answer here.

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