Is pain a sign of cancer?

Yes/No. Some cancers present with pain depending on the organ/ location, and if there is any involvement of nerve roots or nerve plexus. On the other hand, many tumors do not presents with pain.
Pain and Cancer. It can be, but so many non-cancerous conditions, such as arthritis, gallbladder disease, digestive disorders, even the common headache, are associated with pain, that only regular check ups, cancer screenings (pap smear, mammogram, colonoscopy, oral cancer screening, skin surveys, and the like), can evaluate you optimally for possible signs of cancer. Check with your doctor if you are having pain.