We expect nothing but the highest level of professionalism and expertise when we walk into a doctor's office or hospital. And while a vast majority of times we are properly diagnosed and our problems are addressed and we heal, there are times when a doctor or medical facility may fail their patient.
If a failure to diagnose or a delay in a diagnosis leads to a disease progression that otherwise would have been addressed sooner and this leads to a worsened condition, the doctor or medical professionals could be held liable. Doctors often will try to diagnose a condition by doing a "differential diagnosis". This means that he or she will look at the symptoms of a patient and list the different possible illnesses that could be involved.
Generally, it needs to be proven that a doctor's misdiagnosis was an oversight that would not have occurred with other similar doctors. If a doctor's diagnosis did not consider the other differential diagnosis options, or if the doctor did not run the necessary tests or scans to diagnose the condition, the doctor may be held responsible. Such instances can be very difficult to prove, especially in cancer cases, where micro metastasis, or the spreading of cancer cells, can occur for years before an initial tumor is even diagnosed. In such cases, the patient must prove that the worsened prognosis was due to a medical oversight, which may not have even been possible.
As you can see, if you believe that doctor's errors and a failure to diagnose has led to a worsened condition, you will need a strong team on your side to prove these allegations. Often, this can only be done with an experienced firm familiar with medical malpractice and failure to diagnose cases.