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Mammillar and Mamillary are (apparently) used to refer to things that are breast or nipple shaped (but are not breasts or nipples).

The non-OED Oxford dictionaries (for mammillary):

Shaped like or resembling a breast or nipple

The free dictionary (for mammillar):

(Biology) resembling a breast or nipple

The term you're looking for is breast-shaped.

Examples:

Winter Park may buy breast-shaped building on Lee Road (Orlando Sentinel, 2014)

During the colonial and early American periods, the mountain was known as "Mamelle" mountain. "Mamelle" is a name commonly applied in the French-speaking parts of the world to a breast or any breast-shaped hill. (Encyclopedia of Arkansas History & Culture, 2016)

Is the breast-shaped shadow on St. Mary’s Cathedral an accident or a clever prank? (KALW, 2018)

mammiform in British (ˈmæmɪˌfɔːm)

adjective having the shape of a breast

Collins English Dictionary.

https://www.collinsdictionary.com/dictionary/english/mammiform

I would suggest "mammillary", since it appears in the phrase "mammillary body", the usual term for a brain region named for its breast-like shape.

The trigonometric "sine" function derives its name from the Latin "sinus" meaning "bosom". This is itself a translation of the Arabic word "jaib" (also meaning "bosom"). The use of "jaib" is said to be due to phonetic similarity with the original Sanskrit "jiva" for "chord" transliterated into Arabic as "jiba" or "jb", but this would surely have been reinforced by the breast-like shape of this function.

So, if the sine function is breast-shaped, surely we can say the breast is sine-shaped?

Mammaries is the plural to describe the breasts as it comes from 17th Century English (from mamma + -ary)

Mammary glands are glands within the breast which hold milk when lactating, and although the word mammary is used in the medical profession to describe breast tissue in both men and women, hense the word mammogram for male breast cancer testing (see here), the word is only used in the generalised sense when talking of female breasts.

ADJECTIVE

Denoting or relating to the human female breasts or the milk-secreting organs of other mammals.
"mammary tumour viruses".

NOUN

informal

A breast.
"Page Three has become synonymous with mammaries".

Pronunciation
mammary /ˈmaməri/

Websters and Oxford dictionaries both define mound as "A rounded mass projecting from a surface". I would suggest that it is simple, unpretentious,and easily identified as a descriptor of "breast-shaped".

Following tchrist's comment, if it’s Greek you want, while

mas­tos (μαστός) is just a sin­gle teat

and the source for mastectomy,

stethos (στῆθος)

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

cal­lis­tet­hous

for the Bac­trian ver­sion (patterned after 'callipygian') or

cal­li­mas­tian

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).

Or

Tec­tonic

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')