How is a Cancer Diagnosis Made?

Making a cancer diagnosis is simple, yet it can be tricky... let us explain...

In a sense, making the diagnosis of cancer is simple since all it requires is a biopsy, a sample of the diseased tissue, to be analyzed by a pathologist. A trained pathologist can determine if the tissue in question is in fact cancer and, if so, what type of cancer it is. This is generally true of most types of cancer.

One "tricky" aspect of making a cancer diagnosis is that some tumors may be in an area of the body that is difficult to get to in order to take the biopsy. For example, a cancer in the middle of the brain, surrounded by normal brain tissue, may be difficult to get to surgically.

However, often the trickiest part is getting to the point of recognizing that a patient needs a biopsy of a tumor in their body in the first place.

Symptoms of cancer vary tremendously and many are not very specific to cancer and can be caused by many other things. For example, while headache is a vague symptom that is often associated with tumors in and around the brain, millions of people a day experience headache for other reasons and do not have cancer. Therefore, many people can present with vague or non-specific symptoms due to cancer that initially go undiagnosed.

However, when a patient finally comes to medical attention because of symptoms related to the disease, there are a number of tests or studies which can be done to identify a tumor in the body:

History and Physical Examination: Usually the first step in making a diagnosis of cancer is to take a general history and physical examination of the patient. The history is the subjective questioning of the patient about their medical history, the symptoms they are experiencing and any risk factors which may predispose them to cancer. This is followed by a physical examination which is aimed at identifying signs or symptoms the patient is displaying which may be associated with a specific disease. While the history and physical is an important first step in determining the need for further work-up, it rarely results in a final cancer diagnosis on its own .

Blood Testing: Blood tests rarely result in the diagnosis of cancer but can be useful for a few specific types. They may also be helpful in ruling out other diseases which could potentially be causing the patient's symptoms.

Medical Imaging Tests: For most types of cancer, the cancer diagnosis is supported by an imaging test which demonstrates a mass (a tumor) within the body. An imaging test is anything that creates a picture of the insides of the body. Common examples are x-rays, computed tomography scans (CAT or CT scans), magnetic resonance imaging (MRI), ultrasound and positron emission tomography (PET). These imaging studies can show the normal structures within the body as well as abnormal tissues and masses. While it does not 100% confirm that a mass is cancer, it identifies the tumor and helps narrow the diagnosis down and suggest further work-up that may be needed. The specific type of testing that is done depends on the clinical situation and the part of the body which is being imaged.

Ruling out other diseases: The work-up of many cancers includes ruling out other diagnoses, other diseases which could present in a similar way. For example, shortness of breath may be a symptom of lung cancer, yet it could be the symptom of many other diseases including asthma, heart disease and pulmonary embolism. Therefore, work-up and diagnosis of the underlying disease would include a work-up for all these diseases. Because most cancers do not have specific symptoms which are unique to them, most patients will undergo some testing which is directed at diagnosing these other diseases.

Biopsy or Surgical Removal of the Tumor: Once a mass is identified in the body, the final, definitive cancer diagnosis and the type of cancer is only made once some of the abnormal tissue can be sampled and examined by a pathologist. This can include either a limited biopsy, which is a small sampling of the tissue, or a full operation with the goal of removing the entire tumor or as much of it as possible. The extent of biopsy and tumor removal that is indicated depends entirely on the clinical situation in each case and the type of suspected tumor.

Finally, some patients may not have any symptoms related to the cancer. Some of these patients will not come to medical attention until the cancer presents with obvious symptoms. However, in some cases, the cancer diagnosis will be discovered almost by accident. In many cases, the individual receives testing for an unrelated condition and this testing reveals the hidden cancer. For example, an individual may have a CT scan of the abdomen for another reason, and a tumor in the liver or some other organ is seen. This is called an incidentally diagnosed or discovered tumor or an incidental diagnosis. In summary, making a final cancer diagnosis generally depends on a sample of the diseased tissue being sampled and examined by a pathologist. However, the work-up that gets any patient to that point can be quite complicated and variable.