HETEROGENEITY OF METASTATIC GASTRIC NEUROENDOCRINE TUMOR

The purpose of the study was to demonstrate the effect of heterogeneity of a tumor and its metastases on the choice of treatment tactics in a clinical case. A patient with gastric neuroendocrine cancer and liver metastases was examined. According to immunohistochemical analysis, the primary neuroendocrine tumor (NET) of the stomach was highly differentiated (NET, G1). In liver metastases S1, S2, S5, S8, NETs were moderately differentiated (NET, G2), and in S7 NETs were poorly differentiated (NEC, G3), demonstrating the tumor heterogeneity which progressed as the malignant process developed. Only in the low-differentiated NETs (NEC, G3), the reaction with Chromogranin A was negative, which is typical of low-differentiated NET. The reaction with SSTR2 was moderately and sharply expressed in liver metastases S7, S5, S8 and, on the contrary, was nearly undeterminable in the primary NET of the stomach and in liver S1, S2. The clinical case demonstrates the phenomenon of tumor heterogeneity and the associated ambiguity of the results of immunohistochemical research. Therefore, testing of tumors prior to the treatment is of paramount clinical importance for the correct treatment choice and disease prognosis. The development of specific molecular markers for the diagnosis of neuroendocrine tumors remains an actual problem of oncology.