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J Surg Res. 2013 Sep;184(1):221-7. doi: 10.1016/j.jss.2013.04.008. Epub 2013 Apr 25.

Surgery for metastatic neuroendocrine tumors with occult primaries.

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  • 1Department of Surgery, University of Pennsylvania, Philadelphia, Pennsylvania, USA.



Neuroendocrine tumors (NETs) frequently metastasize prior to diagnosis. Although metastases are often identifiable on conventional imaging studies, primary tumors, particularly those in the midgut, are frequently difficult to localize preoperatively.


Patients with metastatic NETs with intact primaries were identified. Clinical and pathologic data were extracted from medical records. Primary tumors were classified as localized or occult based on preoperative imaging. The sensitivities and specificities of preoperative imaging modalities for identifying the primary tumors were calculated. Patient characteristics, tumor features, and survival in localized and occult cases were compared.


Sixty-one patients with an intact primary tumor and metastatic disease were identified. In 28 of these patients (46%), the primary tumor could not be localized preoperatively. A median of three different preoperative imaging studies were utilized. Patients with occult primaries were more likely to have a delay (>6 mo) in surgical referral from time of onset of symptoms (57% versus 27%, P = 0.02). Among the 28 patients with occult primary tumors, 18 (64%) were found to have radiographic evidence of mesenteric lymphadenopathy corresponding, in all but one case, to a small bowel primary. In all but three patients (89%), the primary tumor could be identified intraoperatively.


The primary tumor can be identified intraoperatively in a majority of patients with metastatic NETs, irrespective of preoperative localization status. Referral for surgical management should not, therefore, be influenced by the inability to localize the primary tumor.


Carcinoid; Metastatic neuroendocrine tumor; Occult primary

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