Neuroendocrine Rectal Tumors: Main Features and Management

Abstract

The incidence of neuroendocrine tumors of the rectum has been increasing in the last decades, partly due to improved investigation. They are mostly well-differentiated small tumors with a rather good overall prognosis. In the last few years, some aspects of neuroendocrine tumors have been evolving. In 2010, the World Health Organization proposed a new classification, indicating that these tumors, as a category, should be considered malignant. Afterwards the European Neuroendocrine Tumor Society published their guidelines for the management of colorectal neoplasms. Treatment algorithm is mainly based on tumor size and grading and, in general, well-differentiated rectal tumors <2 cm can be endoscopically resected. Endorectal ultrasound plays a particularly important role by accurately assessing tumor size and depth of invasion prior to resection. There are no specific recommendations on the optimal endoscopic resection method, but data from recent studies suggests that modified endoscopic mucosal resection techniques and endoscopic submucosal dissection have superior complete resection rates.

Poorly differentiated neuroendocrine rectal carcinoma with uncommon immune-histochemical features and clinical presentation with a subcutaneous metastasis, treated with first line intensive triplet chemotherapy plus bevacizumab FIr-B/FOx regimen: an experience of multidisciplinary management in clinical practice

“…Incidence of NECs is 1000 cases annually; 11% within the GI tract [27], with a poor prognosis and commonly arising in the oesophagus and large bowel [28–35]. According to the Surveillance, Epidemiology, and End Results (SEER) database, colorectal NECs has an incidence of 0.2 per 100,000 inhabitants [36].…”

Low-grade Rectal Neuroendocrine Tumor Recurring as Multiple Hepatic Metastasis after Complete Endoscopic Removal: A Case Report

“…Therefore, the World Health Organization and the American Joint Committee on Cancer classified rectal NETs as malignant diseases. 3,4 Many international clinical guidelines have suggested algorithms for treatment and post-treatment surveil-lance tailored to each disease status, but there are always unexpected exceptions in real-world settings. This paper reports a case of small rectal NET that was treated successfully using an endoscopic en-bloc resection.…”

“…Rectal NETs have a more favorable prognosis than adenocarcinoma, for which the 5-year survival rate has been reported to be 75.2-88.3%. 4 The disease stage has the most significant effect on the prognosis. If any lymph node or distant metastasis has occurred, there will be noticeable declines in the 5-year survival.…”

Magnetic Resonance Imaging for Rectal Submucosal Tumours

“…Approximately 34% of neuroendocrine tumours of the gastrointestinal tract (previously known as carcinoid tumours) occur in the rectum, mostly the midrectum. 2,3 They develop from the muscularis mucosa or submucosal layer and are commonly circumscribed. 2,4 Approximately 79% of such tumours are <1 cm and only 5% are >2 cm.…”

“…4 Risk factors for metastatic disease include tumour size, muscularis propria invasion, proliferative index, and lymphovascular and perineural invasion. 3 Patients with a larger tumour are often referred for further imaging before excision. Patients with unfavourable histology after excision are referred for MRI to exclude metastasis in the mesorectum.…”