malignant tumor vs malignant neoplasm

malignant tumor and malignant neoplasm both are nouns.

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

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

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

Other synonyms of malignant tumor include metastatic tumor.

malignant 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