A misdiagnosis is tragic, particularly when a doctor misses a cancer diagnosis. Misdiagnoses are a common type of medical malpractice case, but they can be difficult to prove. An attorney will have to show that the doctor could have detected the illness based on the information they had.
Keep in mind, the doctor may not have known all the patient's symptoms and medical history, leaving them with an incomplete picture of the patient's health. Medical science is not infallible. Just because a cancer diagnosis was missed, it doesn't always mean the doctor could detect the cancer at that time.
Your attorney will need to show that the doctor breached the standard of care. Standard of care typically refers to the accepted way to interpret or treat a patient's symptoms or illness. If a doctor didn't follow that standard of care during the patient's treatment or diagnosis, you may have a case.
An attorney will hire medical experts to review the details of your condition and diagnosis. These experts will need to testify in court that your doctor did (or didn't) do the correct things during your treatment. The doctor being sued will also hire experts to support their side of the case. It is not uncommon for these experts to disagree, so the more evidence supporting your case the better.