Embryonic transcription factors CDX2 and Oct4 are overexpressed in neuroendocrine tumors of the ileum: a pilot study

Current Practices and Novel Techniques in the Diagnosis and Management of Neuroendocrine Tumors of Unknown Primary

Neuroendocrine tumors (NETs) comprise a heterogeneous group of neoplasms in which tumor staging/prognosis and response to treatments depend heavily on accurate and timely identification of the anatomic primary site or NET subtype. Despite recent technological advancements and use of multiple diagnostic modalities, 10% to 14% of newly diagnosed NETs are not fully characterized based on subtype or anatomic primary site. Inability to fully characterize NETs of unknown primary may cause delays in surgical intervention and limit potential treatment options. To address this unmet need, clinical validity and utility are being demonstrated for novel approaches that improve NET subtype or anatomic primary site identification. Functional imaging using Ga-radiolabeled DOTATATE positron emission tomography/computed tomography has been shown to overcome some false-positive and resolution issues associated with octreotide scanning and computed tomography/magnetic resonance imaging. Using a genomic approach, molecular tumor classification based on differential gene expression has demonstrated high diagnostic accuracy in blinded validation studies of different NET types and subtypes. Given the widespread availability of these technologies, we propose an algorithm for the workup of NETs of unknown primary that integrates these approaches. Including these technologies in the standard workup will lead to better NET subtype identification and improved treatment optimization for patients.

High expression of the putative cancer stem cell marker, DCLK1, in rectal neuroendocrine tumors

Doublecortin-like kinase 1 (DCLK1), a microtubule-associated protein, is known to regulate neuronal differentiation, migration and neurogenesis. Recent evidence suggests that the protein is a putative marker for intestinal and pancreatic stem cells, including their cancer stem cell counterparts. The present study conducted immunohistochemical analyses for DCLK1 and the stemness marker, NANOG, in human intestinal neuroendocrine tumors (NETs), as their expression had not been previously investigated in these tumors. Eighteen patients with endoscopically resected rectal NETs were enrolled in the study. The mean age of the patients was 51 years old. The mean diameter of the resected tumors was 5.2 mm, and a histological diagnosis of NET grade G1 was formed for all tumors. Immunohistochemical analysis was performed not only for DCLK1, but also for the known NET markers, synaptophysin, chromogranin A and cluster of differentiation (CD)56. The intensity and distribution of staining were scored on a scale of 0–3 and 0–2, respectively. The sum of the scores was calculated for each specimen. Co-expression of DCLK1 and NANOG was also examined. The mean scores for DCLK1 and synaptophysin were significantly higher than those for chromogranin A (P<0.0001) and CD56 (P<0.01). There were no significant differences in the scores between DCLK1 and synaptophysin or between chromogranin A and CD56. Notably, NANOG was expressed in high quantities in all the tumor tissues studied, showing clear co-expression with DCLK1. In conclusion, DCLK1 may be a novel marker for rectal NET, potentially indicating the presence of the stemness gene product, NANOG.