The morphologic assessment of rectal neuroendocrine tumors

Background and aims: The histopathologic features of rectal neuroendocrine tumors (NETs), including size, lymphovascular invasion, invasion of proper muscle, and mitotic rate, have a limited role to play in determining a treatment plan preoperatively. We aimed to investigate the morphologic parameters associated with metastasis, and to evaluate their predictive value. Methods: Between January 2000 and May 2011, the medical records and endoscopic findings of 468 patients presenting with rectal NETs at the Samsung Medical Center were analyzed retrospectively. All tumors were classified according to size and endoscopic features such as color, shape, contour, and surface change. Results: Twenty-one of the 468 patients (4.5%) with rectal NETs had lymph node (LN) metastasis and 11 patients (2.4%) had distant metastasis. Risk factors for metastasis included tumor size (≥10. mm in diameter), hyperemic change, polypoid lesions, irregular contours, and surface ulceration (. p=0.000). Independent risk factors that were predictive of metastasis on multivariate analysis included tumor size (≥10. mm in diameter), hyperemic change, and surface ulceration. As the number of independent risk factors for metastasis increased, the risk of metastasis rose. Conclusions: Endoscopic features such as hyperemic change, polypoid lesions, irregular contours, and surface ulcers with tumor size ≥10. mm in diameter are associated with metastasis in rectal NETs. In particular, atypical endoscopic features including hyperemic change, and surface ulcer with tumor size ≥10. mm in diameter may help to predict the risk of metastasis of rectal NETs.