| Theme |
Colorectal carcinoid tumors -- New strategy of treatment |
| Title |
Endocrine cell tumors of the gastrointestinal tract -- carcinoid tumor and endocrine cell carcinoma |
| Author |
Mitsuya Iwafuchi |
Division of Pathology, Department of Medical Technology, School of Health Sciences, Faculty of Medicine, Niigata University |
| Author |
Tooru Watanabe |
Division of Pathology, Department of Medical Technology, School of Health Sciences, Faculty of Medicine, Niigata University |
| Author |
Hidenobu Watanabe |
Division of Molecular and Functional Pathology, Department of Cellular Function, Niigata University Graduate School of Medicine and Dental Sciences |
| [ Summary ] |
Endocrine cell tumors (ECTs) of the gastrointestinal tract are divided into two definite groups; carcinoid tumors (CTs) with low-grade atypia and malignancy, and endocrine cell carcinomas (ECCs) (small cell carcinoma: SCC) with high-grade atypia and malignancy. The majority of CTs are hypothesized to derive from immature endocrine cells. There were four hypothesized precursor cells from which ECCs derive; neoplastic endocrine cells in adenocarcinoma, pluripotential stem cells, immature endocrine cells, or CT. We concluded that most ECCs arise from neoplastic endocrine cell clones occurring in the deep mucosal region of the preceding differentiated type (tubular) adenocarcinoma.
In histological examination of ECTs, the first step is a differential diagnosis between CT and ECC. In cases of CT, then, the degree of malignant and metastatic potential for CT should be judged by a combination of histomorphology (tumor size, depth of invasion, cellular and nuclear atypia/pleomorphism, mitotic rate, vascular/perineural invasion) and proliferation rate (Ki-67 index). There are some differences between the Japanese and the WHO (Western) classification systems of ECTs of the gastrointestinal tract. ECTs are divided into two groups in the Japanese system and three in the WHO system. The term CT is used for ECT with or without metastasis or invasion deeper than the muscle proper in the Japanese system, but is used only for ECT with out metastasis or invasion deeper than the muscle proper in the WHO system. Not only the first group (well-differentiated endocrine tumor-carcinoid) but also second group (well-differentiated endocrine carcinoma-malignant carcinoid) in the WHO system, correspond to CT in the Japanese system. ECC (SCC) in the Japanese system includes both ECT composed of small-to interme diate-sized tumor cells (small cell type endocrine cell carcinoma) and those composed of large-sized tumor cells (large cell type endocrine cell carcinoma). On the other hand, the third group (poorly differentiated endocrine carcinoma-SCC) in the WHO system means only ECT composed of small-to intermediate-sized tumor cells. |