On 2015 Oct 23, Miguel Lopez-Lazaro commented:

This article provides a model to explain that virtually every cancer cell within a tumor often contains the same core set of genetic alterations, with heterogeneity confined to mutations that emerge late during tumor growth.

In my opinion, there is a simpler explanation. Recent evidence strongly suggests that cancer arises from normal stem cells. If cancer arises from normal stem cells, all the mutations occurring in these cells before becoming malignant (cancer stem cells, CSCs) will be found in all their progeny, that is, in all the tumor cancer cells. Some tumor cells may lack some of these mutations if they lose during cell division the chromosomes or pieces of chromosomes that bear these DNA alterations. The mutations arising during the self-renewal of CSCs will be found only in the tumor populations derived from these malignant stem cells. In addition to self-renewing, CSCs generate progenitor cancer cells, which divide and produce the bulk of cancer cells within a tumor. The mutations found in few tumor cancer cells probably occur during the division of these progenitor cells. In some cases, the tumor cancer cells may arise from more than one normal stem cell. In these cases, not all the cancer cells within a tumor will share the same core set of genetic alterations (1). Normal and malignant stem cells are defined by their self-renewal capacity and differentiation potential, and have a natural ability to migrate.

(1). Lopez-Lazaro M. Selective amino acid restriction therapy (SAART): a non-pharmacological strategy against all types of cancer cells. DOI: 10.18632/oncoscience.258

On 2015 Oct 23, Miguel Lopez-Lazaro commented:

This article provides a model to explain that virtually every cancer cell within a tumor often contains the same core set of genetic alterations, with heterogeneity confined to mutations that emerge late during tumor growth.

In my opinion, there is a simpler explanation. Recent evidence strongly suggests that cancer arises from normal stem cells. If cancer arises from normal stem cells, all the mutations occurring in these cells before becoming malignant (cancer stem cells, CSCs) will be found in all their progeny, that is, in all the tumor cancer cells. Some tumor cells may lack some of these mutations if they lose during cell division the chromosomes or pieces of chromosomes that bear these DNA alterations. The mutations arising during the self-renewal of CSCs will be found only in the tumor populations derived from these malignant stem cells. In addition to self-renewing, CSCs generate progenitor cancer cells, which divide and produce the bulk of cancer cells within a tumor. The mutations found in few tumor cancer cells probably occur during the division of these progenitor cells. In some cases, the tumor cancer cells may arise from more than one normal stem cell. In these cases, not all the cancer cells within a tumor will share the same core set of genetic alterations (1). Normal and malignant stem cells are defined by their self-renewal capacity and differentiation potential, and have a natural ability to migrate.

(1). Lopez-Lazaro M. Selective amino acid restriction therapy (SAART): a non-pharmacological strategy against all types of cancer cells. DOI: 10.18632/oncoscience.258