substernomastoid

sub·ster·no·mas·toid

(sŭb'ster-nō-mas'toyd),
Beneath the sternomastoid muscle; denoting a group of deep cervical lymph nodes.

substernomastoid

(sŭb-stĕr-nō-măs′toyd) [″ + ″ + Gr. mastos, breast, + eidos, form, shape]
Beneath the sternomastoid muscle.