Following tchrist's comment, if it’s Greek you want, while
mastos (μαστός) is just a single teat
and the source for mastectomy,
is the entire bosom in full (source for stethoscope). There’s also
bathukolpian, bathycolpian < βαθύκολπος,
both of which already exist — but perhaps you might settle for
for the Bactrian version (patterned after 'callipygian') or
for the dromedary. Speaking of which, Latin and her children have supplied English with a huge whole lot of words about this that nobody has mentioned yet, like
mammate, mammeated, mamelonated (for teeth protuberances), mammatous (for clouds).
is quite nice once you strike its spurious letter. Guess which one!
For the record, none of these are really used for the way that you presumably intend, but they surely should (spellcheck barfs over all these suggestions except for 'tectonic')