In our current prospective cohort, we observed a subset of cases that harbored two or more additional clonal driver mutations, aside from VHL. Simulated models of tumor growth (Reiter et al., 2013) suggest that just one additional driver will significantly increase the growth rate, and we utilized WGS molecular clock timing data (see the accompanying paper by Mitchell et al., 2018) to test this hypothesis in our data. The gene discussed is VHL; the disease is neoplasm.