FH and neoplasm: Subsequent studies of PGLs/Pheos and GISTs with SDH complex subunit gene mutation demonstrated a CpG island methylator phenotype (CIMP) and identified a single PGL sample with the CIMP phenotype that demonstrated an FH mutation, which could not be confirmed as germline or somatic [23, 24] Furthermore, a comparative study demonstrated that the patterns of methylation associated with loss of succinate dehydrogenase activity were similar but not identical between different tumor tissue types, such as PGLs verses GISTs [24].