Liver cancer, gross specimen of malignant carcinoids in the liver. Carcinoid tumours are slow-growing but often malignant, and are of neuroendocrine origin. They originate in the APUD cells (amine producing and precursor uptake and decarboxylation). These tumours metastasized from carcinoids of the gut, metastasis being the transfer of disease from one organ or part to another not directly connected with it. All malignant tumours have the capacity to metastasize. The commonest malignant growths found in the liver do in fact arise from cancers in other organs. Once a cancer has spread beyond its site of origin, the prognosis is poor.