metastatic tumor vs malignant neoplasm

metastatic tumor and malignant neoplasm both are nouns.

Word	Noun	Adjective	Verb	Adverb
metastatic tumor	Yes	No	No	No
malignant neoplasm	Yes	No	No	No

As nouns, metastatic tumor and malignant neoplasm are synonyms defined as:

metastatic tumor and malignant neoplasm: a tumor that is malignant and tends to spread to other parts of the body

Other synonyms of metastatic tumor include malignant tumor.

metastatic tumor (noun)	malignant neoplasm (noun)
a tumor that is malignant and tends to spread to other parts of the body	a tumor that is malignant and tends to spread to other parts of the body