SDHB and neoplasm: Given that the data obtained in murine and cellular models support that SDH loss of function do not directly activate the HIF-1α pathway, that HIF-1α nuclear accumulation is only observed in about 38% of tumor cells in SDHxm-PGLs, and that these tumors show mild miR-210 over-expression, we postulate that HIF-1α up-regulation in these tumors is a late event that it is favored by SDHx mutations but is triggered by still undefined biochemical or genetic event/s.