benign tumor vs benign tumour

benign tumor and benign tumour both are nouns.

Word	Noun	Adjective	Verb	Adverb
benign tumor	Yes	No	No	No
benign tumour	Yes	No	No	No

As nouns, benign tumor and benign tumour are synonyms defined as:

Other synonyms of benign tumor include nonmalignant neoplasm, nonmalignant tumor, nonmalignant tumour.

benign tumor (noun)	benign tumour (noun)
a tumor that is not cancerous	a tumor that is not cancerous