melanoma vs skin cancer

melanoma and skin cancer both are nouns.

Word	Noun	Adjective	Verb	Adverb
melanoma	Yes	No	No	No
skin cancer	Yes	No	No	No

As nouns, skin cancer is a hypernym of melanoma; that is, skin cancer is a word with a broader meaning than melanoma:

melanoma: any of several malignant neoplasms (usually of the skin) consisting of melanocytes
skin cancer: a malignant neoplasm of the skin

melanoma (noun)	skin cancer (noun)
any of several malignant neoplasms (usually of the skin) consisting of melanocytes	a malignant neoplasm of the skin