Related Experiment Video
Updated: May 11, 2026
Modified Radical Neck Dissection for Cervical Metastasis
Published on: February 20, 2026
Surgery for metastatic neuroendocrine tumors with occult primaries
Edmund K Bartlett1, Robert E Roses, Meera Gupta
1Department of Surgery, University of Pennsylvania, Philadelphia, Pennsylvania, USA. Edmund.Bartlett@uphs.upenn.edu
Introduction:
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.
Materials And Methods:
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.
Results:
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.
Conclusion:
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.
Insights
Locating primary neuroendocrine tumors (NETs) preoperatively is challenging, even with metastases. Intraoperative identification is successful in most cases, guiding surgical referral decisions for metastatic NET patients.
Area of Science:
- Oncology
- Radiology
- Surgical Oncology
Background:
- Neuroendocrine tumors (NETs) often present with metastases, complicating preoperative localization of the primary tumor, especially in the midgut.
- Conventional imaging can identify metastases but frequently fails to pinpoint the primary NET site before surgery.
Purpose of the Study:
- To evaluate the efficacy of preoperative imaging in localizing primary neuroendocrine tumors (NETs) in patients with known metastatic disease.
- To determine if the inability to localize a primary NET preoperatively impacts intraoperative findings and subsequent surgical referral.
Main Methods:
- Retrospective review of 61 patients with metastatic NETs and intact primary tumors.
- Classification of primary tumors as localized or occult based on preoperative imaging.
- Calculation of imaging modality sensitivity and specificity; comparison of patient characteristics, tumor features, and survival between localized and occult primary groups.
Main Results:
- 46% of primary NETs were not localized preoperatively despite a median of three imaging studies.
- Occult primary NETs were associated with a significant delay (>6 months) in surgical referral.
- Mesenteric lymphadenopathy was observed in 64% of occult primary cases, suggesting a small bowel origin.
- Intraoperative identification of the primary tumor was successful in 89% of cases, regardless of preoperative localization.
Conclusions:
- Intraoperative identification of primary NETs is feasible in most patients with metastatic disease, irrespective of preoperative imaging results.
- The inability to localize a primary NET preoperatively should not deter surgical referral for metastatic NETs.