SDHD and adrenal gland pheochromocytoma: Although we investigated gene mutations of only SDHA, SDHB, SDHC, SDHD, FH and RET genes in this cohort, in comparison to SDHB gene mutant with amino acid sequence variation with metastatic PCC/PGL with a PASS greater than 4 or a GAPP grade of poorly differentiated type, some PCC/PGL with a PASS below 4 or a GAPP grade of well to moderately differentiated types had a synonymous SDHB gene mutation without amino acid sequence variation and RET gene mutation, indicating there might be different signaling between metastatic and non-metastatic PCC/PGL.