On the Concept of Tumor Homogeneity

To the Editor: Heterogeneity of tumors is a topic that has received much attention in recent years. First, studies that applied sequencing and other molecular techniques on different tumoral areas, like the landmark paper by the group of Swanton,1 have shown that mutations and other molecular alterations can be heterogenously present within a tumor and it metastases, thereby possibly hindering biomarker and targeted therapy development [...