Introduction: Gastroenteropancreatic neuroendocrine tumours (GEP NETs) are a heterogenous group of tumours of various clinical presentations. Proliferative activity of tumour cells is an essential parameter determining the course of the disease and affecting the prognosis. The Ki-67 antigen is an important marker of cell proliferation, which shows activity in all the phases of the cell cycle, excluding the G0 phase.
Aim of the study: To assess the expression of Ki-67 in GEP NETs and to examine the association of Ki-67 with the stage of the tumour (tumour size, presence of metastases) and the hormonal function of the tumour.
Material and methods: We included 61 patients with GEP NETs (25 males and 36 females aged between 20 and 82 years [mean age: 56 years]). The proliferative activity was examined in paraffin blocks containing surgically removed tumour samples and in core-needle biopsies of primary and metastatic tumours. The presence of the Ki-67 antigen was assessed by immunohistochemistry using MIB‑1 monoclonal antibodies. Based on the Ki-67 proliferative index we determined the tumour grade. In addition, we determined the tumour stage according to the TNM classification. In all the subjects we determined the levels of the non-specific NET marker (chromogranin A) and of specific NET markers (serotonin, insulin and gastrin in the blood and 5‑hydroxyindoleacetic acid [5‑HIAA] in 24-hour urine).
Results: The diagnoses of low-grade (Ki‑67 ≤ 2%), intermediate-grade (Ki-67 3-20%) and high-grade (Ki‑67 > 20%) NET were established in 38, 12 and 11 patients, respectively. Metastatic disease was diagnosed in 36/61 patients. A significantly higher expression of K-67 was observed in patients with metastatic disease (p = 0.01). A positive correlation was demonstrated between Ki-67 and the stage of the disease (p = 0.01) and between the histologic grade of the tumour and the stage of the disease (p = 0.01). No association between Ki-67 and the levels of chromogranin A, serotonin, insulin, gastrin and 5-HIAA was shown. There was also no difference in Ki-67 expression relative to the location of the primary tumour and the tumour size.
Conclusions: The Ki-67 proliferative index is an essential parameter predicting the course of GEP-NETs.