Light micrograph of a section through human lung tissue showing a neuroendocrine tumour of the lung. Neuroendocrine tumours are cancers that begin in specialised cells called neuroendocrine cells. These cells have traits similar to those of nerve cells and hormone-producing cells. Neuroendocrine tumours are rare and occur anywhere in the body, but most often in the lungs. There are many types, some grow slowly while others grow quickly.