My sons bone cancer symptoms were overlooked for years and he died as a result. Is the hospital liable for negligence?

Bone cancer symptoms, which include bone pain and an increased number of fractures in the bones, may not be felt or noticed until the bone cancer has been developing for a long period of time. This is because the bones are, of course, inside of the body and you can't see cancer growing there like you can on a breast or somewhere more external and visible. This doesn't mean that the hospital definitely cannot be sued, however. Whether or not you will be able to hold the hospital responsible for failing to see the symptoms of bone cancer will depend on whether the hospital was negligent in not seeing those signs. 

Negligence in medical malpractice is judged by using a reasonable professional standard. For a hospital to be negligent, it must have provided care that was below the level that a reasonable hospital would have. So, if your son was repeatedly breaking or fracturing bones and constantly complaining of bone pain and you took him in to the hospital multiple times, a reasonable hospital might have had procedures in place to identify that further testing for bone cancer should have been done. In such a case, if your hospital ignored the symptoms, that might be viewed as an unreasonable breach of the duty of care owed to you as a patient, and the hospital may be viewed as negligent.

Assuming the hospital is viewed as negligent, the next step will be proving the negligence led to the damages- aka that your son might not have died, or might have lived longer or suffered less pain if the hospital had acted more carefully. This too can be somewhat hard to prove. 

Clearly, with the difficulties inherent in your case, you will need a good lawyer. Consult with one as soon as possible to find out if you will be able to hold the hospital responsible for what they did to your son or not.