Neuroendocrine liver metastases: contributions of endoscopy and surgery to primary tumor search.

Neuroendocrine tumors (NETs) are diagnosed with increasing frequency and patients often present with liver metastases at the time of diagnosis. Apart from treatment of the metastases, resection of the primary tumor at an early phase is recommended to prevent complications, although it may be difficult to locate, especially in patients with functionally inactive NETs. Small and multifocal tumors in the jejunum and ileum represent a particular challenge. Primary hepatic neuroendocrine carcinoma is extremely rare and is diagnosed only after exclusion of other primary tumors. Therefore, some uncertainty may remain, as small non-hepatic primary tumors may escape detection. Diagnostic work-up in these patients includes biochemical assays and imaging modalities (also comprising specific techniques of scintigraphy and positron emission tomography). This editorial highlights the contributions of endoscopy and operative exploration to the search for the primary tumor. Besides esophago-gastro-duodenoscopy, endoscopic ultrasonography, colonoscopy and bronchoscopy, special endoscopic techniques such as balloon enteroscopy or capsule endoscopy are used with growing experience. Compared with balloon enteroscopy, capsule endoscopy is non-invasive and better tolerated, but it cannot localize a lesion precisely and does not allow biopsy or removal of lesions. Before proceeding to surgery, a discussion of the findings by a tumor board should be a standard procedure. Improvements in diagnostic tools have created new perspectives for the detection of obscure primary tumors in patients with neuroendocrine liver metastases, and these searches are best coordinated by a multidisciplinary team.