Unintentional weight loss. If you have not made any changes to your eating habits or physical exercise routine, and are still losing weight, this may indicate that you are under significant stress or have a thyroid problem. Unintentional weight loss that adds up to more than ten pounds is something that should be looked in to. This could also be an indicator of some type of cancer, however this is much less common. Your doctor will assess this by doing blood tests and certain scans such as a CT scan or PET scan.

Difficulty swallowing. If you have persistent difficulty swallowing, which is also accompanied by weight loss or vomiting, you should see your doctor right away. This could be an indication of throat cancer or stomach cancer. Your doctor will do a throat exam and barium X-ray.

Blood in urine or stool. Blood in your urine or stool may indicate the initial signs of bladder cancer, kidney cancer, or colon cancer. More often than not, the blood is related to something other than one of these types of cancer such as hemorrhoids or a urinary infection. Either way, it is best to determine the underlying cause.

Urination problems. Many men have issues urinating as they get older. This includes needing to urinate more frequently (especially at night), dribbling, leaking, difficulty initiating urination, or having a weak stream. These are often caused by an enlarged prostate. However, in some cases it may be an indication of prostate cancer. Your doctor will most likely do a PSA test, digital rectal exam, and urine analysis to see what is causing the problem. 

Changes in your skin. If you notice a change in the size, shape, or color of a mole or other spot on your skin, you should see your doctor as soon as possible. Changes in your skin like this may indicate skin cancer, which is one of the most common cancers. Your doctor may do a skin biopsy to analyze the abnormal tissue.

Abnormal change in your testicles. Get checked out if you notice a new lump, heaviness, or any other abnormal change in your testicle. This may be an indication of testicular cancer. Testicular cancer can be an aggressive disease which must be treated promptly. Your doctor will do a physical exam, blood tests, and an ultrasound of your scrotum.