What are the most frequent signs of cancer?

Organ&CancerSpecific. Cancer signs are usually related to the organ where the cancer developed and any organs which may be secondarily involved. Advanced cancers may cause loss of appetite, weight loss, muscle wasting, and/or lethargy. In general, the best way to diagnose a cancer is before signs/symptoms develop--that is the purpose of screening tests like mammography, colonoscopy, etc.
Cancer. There is no easy answer to this as each cancer has a different assortment of symptoms. Skin cancer would be totally different than ovarian cancer or lung cancer or even brain cancer. Any unusual symptoms should be checked out with your doctor.