SDHD and neoplasm: Moreover, since SDHD has two modes of inheritance—paternal (SDHD-pi), which contributes to the majority of transmissions, and maternal (SDHD-mi), which is <5% [64], the grade A recommendation is to perform screening for the presence of a tumor once the mutation (SDHA, SDHB, SDHC or SDHD-pi) is identified in an asymptomatic carrier, and to perform genetic screening only when tumor screening is considered.