Tumour cell cannibalism is a long-s

Tumour cell cannibalism is a long-standing story that was virtually neglected for up to a century but is now receiving increasing attention. The first reports describing the presence of cells within other cells in tumour tissues emerged approximately 120 years ago1,2. For decades after these few reports, cannibalism was considered only a curiosity or simply a matter for histopathologists, with the literature consisting mostly of cytopathological reports. From a mere cytological point of view, cannibalism was recognized when cell preparations or tumour tissues contained cells with a crescent-shaped nucleus in turn containing another smaller cell, often contained within a large vacuole. The crescent shape of the nucleus was due to the cell-containing vacuole displacing the nucleus towards the cell periphery. This morphological appearance of cannibalism led to the emergence of imaginative terminology such as ‘bird’s-eye cells’3 and the more common ‘cell-in-cell’4.