According to the WHO classification in 2000, distinction was made between well-differentiated neuroendocrine tumours (benign behaviour or uncertain malignant potential, <2% Ki67 positive cells), well-differentiated neuroendocrine carcinomas (low grade malignancy, presence of metastasis and/or invasiveness), and poorly differentiated neuroendocrine carcinomas of high-grade malignancy (usually small cell, >15% Ki67 positive cells) [3]. This evidence concerns the gene MKI67 and neuroendocrine carcinoma.