Cancer of the small intestine, gross specimen. The tumour is a mass of yellow mucosal nodules obstructing the bowel, having metastasized from a primary cancer of the lung. Metastasis is 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 brown pigmentation is due to accumulation of pigment-laden macrophages. Macrophages are a type of phagocyte that engulf dead cells, foreign substances and other debris. Cancer of the small intestine is uncommon.