Midenin nöroendokrin tümörlerinde P-16 ekspresyonu

Abstract

Background and Aims: Gastrointestinal neuroendocrine tumors are rarely seen tumors of the gastrointestinal tract. Stomach-localized neuroendocrine tumors account for just 6% of the so-called tumors. The World Health Organization classifies these tumors into three groups based on their histopathological features, as follows: well-differentiated neuroendocrine tumor, well-differentiated neuroendocrine carcinoma and poorly-differentiated neuroendocrine carcinoma. While well-differentiated neuroendocrine tumors have significantly good prognosis, poorly-differentiated neuroendocrine carcinomas have a highly malignant course. Because there is no histological difference between a well-differentiated endocrine tumor and a carcinoma, a useful marker is needed in order to reveal the tumor behavior. This research aimed to investigate the presence of P-16 expression in tumors of the stomach, which show some similarities to lung small cell carcinoma, in which P-16 has been found to be a helpful guide. Materials and Methods: Toward this aim, 20 cases who underwent surgical stomach resection or endoscopic polypectomy from 2004-2008 were retrospectively analyzed and included in the study. P-16 expression of the cases was calculated as a percentage (%). Results: Among the 20 patients, 15 (75%) had well-differentiated neuroendocrine tumor, whereas 2 (10%) had well-differentiated neuroendocrine carcinoma and 3 (15%) had poorly-differentiated neuroendocrine carcinoma. P-16 scores were found to be 14.4%, 15% and 90%, respectively. Although no statistical difference was found between well-differentiated neuroendocrine tumor and well-differentiated neuroendocrine carcinoma regarding P-16 expression, a significant difference was observed with poorly-differentiated neuroendocrine carcinoma (p=0.007, MannWhitney U test) No correlation was found between P-16 expression and clinicopathological features like age, sex, location of the tumor in the stomach, invasion, atrophy, intestinal metaplasia, endocrine cell hyperplasia, multicentric configuration, and capacity for relapse. Conclusion: In conclusion, overexpression of P-16 may provide support in differentiating tumors with low malignant potential from the highly potential ones, especially in small endoscopic biopsies in which a limited number of tumor cells are being observed. However, these tumors, rarely seen and mostly known as having a low malignant potential, should be investigated in multicenter studies and with longer follow-up periods.