**Acknowledgements**

The authors want to thank Marcial García Rojo, Gloria Bueno and Jose Benavent for technical support on digital pathology. This study was supported by the FIS contracts PI10/00015 and PI14/01008 and RTICC contract RD12/0036/0020, grants from the ISCIII & FEDER (European Regional Development Fund), Spain. The authors declare no conflict of interest.
