Discovering intratumor heterogeneity: the next frontier for pathologists.

Discovering intratumor heterogeneity is a crucial issue in modern oncologic medicine. Highly sophisticated technology such as high-throughput DNA sequencing has demonstrated the real dimension of the problem. The overwhelming majority of malignant tumors show high levels of intratumor heterogeneity when thoroughly studied. Intratumor heterogeneity develops both in temporal and spatial domains and its distribution is not deterministic making each case truly unique and unrepeatable. Pathologists are main actors in intratumor heterogeneity detection since they are the medical specialists who sample the tumors. Recent evidences have shown that currently applied sampling protocols are insufficient for a reliable intratumor heterogeneity detection. Pathologists must adapt classic sampling to the new times thus continuing being key pieces in the multidisciplinary approach to neoplasia that modern medicine demands.