Full Idea
A tumour is not an organism (or a parasite) and there is no self-regulating event that is its life. It does not fill one space, but is a locus within which a certain sort of thing is happening: the spreading of a certain sort of (mass-term) life.
Gist of Idea
A tumour may spread a sort of life, but it is not a life, or an organism
Source
Peter van Inwagen (Material Beings [1990], 09)
Book Reference
Inwagen,Peter van: 'Material Beings' [Cornell 1995], p.88