Small Bowel Carcinoid (NE Tumor, Grade 1, WHO 2010)
Carcinoid forming a polypoid mass at the ileo-cecal junction. In the small bowel, ileum is the most common site of involvement, followed by jejunum and distal duodenum. The classification of neuroendocrine tumors of the gastrointestinal system has been in a state of flux recently. The 2010 Classification of Neuroendocrine Tumors of Gastroenteropancreatic system proposed by the European Neuroendocrine Tumour Society and WHO takes into account mitotic rate and Ki-67 proliferation index: Neuroendocrine Tumor, Grade 1 has <2 mitoses/10HPF, and upto 2% Ki-67 labeling index. It is synonymous with carcinoids; Neuroendocrine Tumor, Grade 2 has 2-20 mitoses/10HPF, OR 3%-20% Ki-67 labeling index; Neuroendocrine Carcinoma (Grade 3) has >20 mitoses/10HPF, OR >20% Ki-67 labeling index. It includes large cell neuroendocrine carcinoma and small cell carcinoma.