Classification and Locoregional Treatment of Rectal Neuroendocrine Tumors

Abstract

A 43-year-old male presented to his primary care physician's office with a complaint of painless rectal bleeding with a concomitant weight loss of 10-15 pounds and intermittent abdominal pain. Endoscopic evaluation was remarkable for a 5 mm rectal polyp roughly 10 cm from the anal verge. Resection was performed and the pathology was consistent with a low-grade neuroendocrine/carcinoid tumor. Immunostaining for synaptophysin, chromogranin, CD56, and CAM5.2 were positive while staining for CK20 was negative. Given the absence of metastasis on radiographic and endoscopic evaluation, the patient was managed conservatively thereafter with observation. Despite having an indolent clinical course, resection is recommended for all rectal neuroendocrine tumors. Locoregional endoscopic resection versus radical resection can be used for adequate tissue removal depending on the characteristics of the tumor and the degree of invasion.

Keywords: endoscopic mucosal resection; endoscopy; gastroenterology; malignancy; rectal neuroendocrine tumor.

Figure 1. Histopathology showing mucosal glands overlying the submucosal carcinoid tumor

Figure 2. High-power view showing nests and cords of cells with monomorphic nuclei and stippled chromatin

Figure 3. Immunohistochemical staining of slide demonstrating positivity to chromogranin

Figure 4. Positive immunohistochemical staining for synaptophysin