cystic mastitis vs fibrocystic disease of the breast

cystic mastitis and fibrocystic disease of the breast both are nouns.

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

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

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

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

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