mastectomy (n.)

before vowels mast-, word-forming element meaning "female breast, mammary gland," from Greek mastos "woman's breast," from madan "to be wet, to flow," from PIE *mad- "wet, moist, dripping" (source also of Latin madere "be moist;" Albanian mend "suckle;" see mast (n.2)).

word-forming element meaning "surgical removal," from Latinized form of Greek -ektomia "a cutting out of," from ektemnein "to cut out," from ek "out" (see ex-) + temnein "to cut" (from PIE root *tem- "to cut").