After a recent river-raft outing, mary experienced severe itching on her back and noticed redness and swelling around a lesion in the area. her back was also sunburned. at first mary thought the lesion was a bug bite and treated it with topical application of calamine and aloe lotion for the burn. when the itching and redness of the lesion did not subside, she went to see her physician. on examination, the physician noticed a raised reddish lesion with irregular borders and found other moles on mary's legs, arms, and back. he referred mary to a dermatologist who performed a biopsy that confirmed suspicion of a malignant melanoma. in mary's case, as in many cases, melanomas often arise in: