male chest vs pectus

male chest and pectus both are nouns.

Word	Noun	Adjective	Verb	Adverb
male chest	Yes	No	No	No
pectus	Yes	No	No	No

As nouns, pectus is a hypernym of male chest; that is, pectus is a word with a broader meaning than male chest:

male chest: the chest of a man
pectus: the part of the human torso between the neck and the diaphragm or the corresponding part in other vertebrates

Other hypernyms of male chest include chest, thorax.

male chest (noun)	pectus (noun)
the chest of a man	the part of the human torso between the neck and the diaphragm or the corresponding part in other vertebrates