fibrocystic breast disease vs cystic mastitis

fibrocystic breast disease and cystic mastitis both are nouns.

Word	Noun	Adjective	Verb	Adverb
fibrocystic breast disease	Yes	No	No	No
cystic mastitis	Yes	No	No	No

As nouns, fibrocystic breast disease and cystic mastitis are synonyms defined as:

fibrocystic breast disease and cystic mastitis: the presence of one or more cysts in a breast

Other synonyms of fibrocystic breast disease include cystic breast disease, fibrocystic disease of the breast.

fibrocystic breast disease (noun)	cystic mastitis (noun)
the presence of one or more cysts in a breast	the presence of one or more cysts in a breast