Does Melanoma Cause Hot Body With Growing Lump Underarm?

My mother in law has an untreatable melanoma. The "lump" under her left arm has increased in size probably 7 times since she was diagnosed in July. She also is probably stage 5 or 6 of Alzheimers. She was getting so hot this evening that she took off her shirt. Does the melanoma cause this? Any recommendations for pain medication? She and her husband won't allow hospice come to help her manage the pain!