While there are obviously much more terrible things associated with having cancer, sweating is on the list of symptoms with this disease. Doctors don't fully understand why this is but theorize that the sweating may be associated with the body trying to fight the cancer. Some types of cancer cause sweating more than others, including bone cancer, liver cancer, leukemia and lymphoma [source: Cancer Research UK].
It's not always the cancer itself causing excess perspiration. The sweating can be a secondary symptom associated with cancer medications, infections associated with the disease and hormone changes. Morphine and chemotherapy can cause patients to get hot flashes and sweat. Infections are probably one of the most common reason for cancer-induced sweating. The fevers that come with infections cause the body to try to cool itself, kicking those sweat glands into high gear.
And just like hormone changes in menopause and hyperthyroidism can cause sweating, hormone changes associated with cancer and its treatments (chemo, radiation and others) can bring on serious perspiration. In fact, certain treatments for breast and prostate cancer can actually induce menopause or menopause-like effects causing hot flashes and sweating.