Cancer stem cell hypothesis
Read the draft explanation
How can a tumour have a clonal origin yet contain very different cancer cells? The cancer stem cell hypothesis offers one explanation. A self-renewing tumour-cell population can maintain itself while producing the heterogeneous cancer-cell lineages that make up the tumour.
Self-renewal means preserving that tumour-propagating capacity through cell division. It is more than rapid proliferation. Cancer stem cells are defined by what they can do; a marker alone does not establish the function.
If this population survives treatment, it may provide a reservoir for regrowth, recurrence or later metastasis. Therapy may therefore need to target these cells as well as the tumour bulk. The model and resistance mechanisms vary between tumour types. Stem-like populations have also been investigated in canine osteosarcoma cell lines.
References
Johnston & Tobias, Veterinary Surgery: Small Animal, 2nd ed., ch. 25; Clarke et al. 2006, doi: 10.1158/0008-5472.CAN-06-3126; Wilson et al. 2008, Vet J 175:69–75.