NISCH and neoplasm: To further investigate intra-tumor heterogeneity, a subset of 20 of the variants detected by exome sequencing was validated by Sanger sequencing in the four original samples (N, P1, IR1, ER1) and in nine additional FFPE samples of tumor implants representing different regions of the primary tumor and recurrences (P2-P6, IR2, ER2-ER4) (Fig. 4a).