Neuroendocrine neoplasms of unknown primary site
- John D Hainsworth, MD
John D Hainsworth, MD
- Chief Scientific Officer
- Sarah Cannon Research Institute
- F Anthony Greco, MD
F Anthony Greco, MD
- Medical Director
- Sarah Cannon Cancer Center
- Jonathan R Strosberg, MD
Jonathan R Strosberg, MD
- Associate Professor
- Department of Gastrointestinal Oncology
- H. Lee Moffitt Cancer Center
- Section Editors
- James R Jett, MD
James R Jett, MD
- Section Editor — Lung Cancer
- Professor of Medicine Emeritus
- National Jewish Health
- Richard M Goldberg, MD
Richard M Goldberg, MD
- Section Editor — Gastrointestinal Cancer
- Professor of Medicine
- The James Cancer Hospital and Solove Research Institute
- Associate Director of Outreach
- Comprehensive Cancer Center
- The Ohio State University Medical Center
Cancer of unknown primary site (CUP) is a relatively common clinical entity, accounting for 4 to 5 percent of all invasive cancers . Within this category, tumors from many primary sites with varying biology are represented. Neuroendocrine neoplasms constitute less than 5 percent of all CUPs . (See "Overview of the classification and management of cancers of unknown primary site".)
Neuroendocrine tumors (NETs) are a heterogeneous group of neoplasms that differ in biologic behavior, histologic appearance, and response to treatment (table 1). Several types of these neoplasms (eg, well-differentiated NET of the tubular gastrointestinal tract [carcinoid tumors] and pancreas [pancreatic NETs or PNET], medullary thyroid cancers, pheochromocytomas) are characterized by slow growth and frequent secretion of hormones or vasoactive substances [3-5]. In most cases, these tumors also have typical histologic appearance and are accurately diagnosed with standard pathologic methods (light microscopy and immunohistochemical staining). Others, as typified by small cell carcinoma of the lung, are highly aggressive neoplasms, classified as neuroendocrine carcinomas, and are usually advanced when diagnosed. (See "Pathology, classification, and grading of neuroendocrine tumors arising in the digestive system".)
NETs of unknown primary site are relatively uncommon, accounting for 10 to 13 percent of all NETs:
●In a review of over 35,000 patients diagnosed with NETs over a 31-year period (most had well-differentiated tumors arising from the gastrointestinal tract), a primary site could not be found or classified in only 13 percent .
●In another series of 750 patients with NET seen over a 24-year period at a single institution, 82 (10 percent) were of unknown primary site .
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