A number of methods are used to confirm a diagnosis of cancer.
A cancer may be suspected for a variety of reasons, but the definitive diagnosis of most malignancies must be confirmed by microscopic examination of the cancerous cells by a pathologist. The procedure of obtaining cells and/or pieces of tissue, and their examination, is referred to as a biopsy. The tissue diagnosis indicates the type of cell that is proliferating, its severity (degree of dysplasia) and its extent and size. Cytogenetic and immunohistochemistry tests may provide information about the future behaviour of the cancer and the best treatment.
Biopsies are obtained in a number of different ways depending on the type of tissue required.
Fine Needle Aspiration Cytology (FNAC)
Fine Needle Aspiration Biopsy
Myth About Biopsy
It is generally thought that cancer spreads after biopsy. It is not true. If do not make the diagnosis it will keep growing and may spread. If treatment is started after biopsy it does not spread however if one does not get treatment it may grow faster.
Bone marrow tests
Bone marrow tests are used in the diagnosis of leukaemia and lymphoma.
A sample of bone marrow is mostly taken from hip bone. The procedure usually involves a general anaesthetic. A needle is inserted through the skin and into the centre of the bone as this contains the marrow. Samples of the marrow cells are then aspirated into the syringe.The bone marrow are then analysed under a microscope to find the abnormal cells.
Myth About Bone Marrow Examination
It is a dangerous procedure can harm the child. It is not true. The procedure is usually done under anesthesia and child does not feel any pain during procedure. He may feel some pain after recovery. It does not harm child at all.
Isotope bone scan
An isotope bone scan involves injecting a small amount of a radioactive substance into a peripheral vein. The radioactive substance migrates through the vascular system, therefore the whole skeleton can be reviewed rather than only the local site. The patient will then undergo X-ray scans of the whole of their skeleton.
Isotope bone scans are used in the diagnosis of primary bone tumours. Bone is also a common site of metastases (secondary cancers). Areas of abnormal bone can be identified as they absorb more of the radioactive substance than normal bone and these areas show up clearly on the X-ray films
MRI (Magnetic Resonance Imaging) & CT (Computerised Tomography)
Both of these investigations are used frequently in the diagnosis and staging of cancer. The scans themselves are very different and the decision regarding their use is based on the part of the body being examined, the accessibility and availability of the scanner and the tolerability of the patient.
An MRI scanner uses magnetic fields rather than images to build up a 3-dimensional picture of part of the body. MRI is particularly useful when looking at the brain, spinal cord and nerves and soft tissue structures such as the heart, lungs, liver and other organs. MRI does not give good images of the chest due to artefacts caused by the continually beating heart. The scan generally lasts for about 30 minutes depending on the part of the body being examined.
MRI scans are used in the diagnosis of brain tumours, lymphoma, neuroblastoma and Wilms’ tumour (nephroblastoma).
CT (Computerised Tomography)
CT scanners use X-rays to build up a 3-dimensional picture of an area of the body. The spiral CT is much faster than conventional CT, making it increasingly acceptable to patients who are unable to tolerate lengthy scans. A modern CT scan can often be performed in considerably less than 1 minute. The scan data is collected by an X-ray tube rotating continuously around the patient while the examination table advances at a constant rate. Unlike conventional CT, this spiral path ensures that there are no gaps between images. CT scanning is presently preferred to Magnetic Resonance Imaging (MRI) due to its general greater availability, its acceptability to patients and the significant difference in cost. As CT scans are not affected by the heart, they are able to provide good images within the chest.
CT scans are used in the diagnosis of brain tumours, lymphoma, neuroblastoma and Wilms’ tumour (nephroblastoma).
PET (Positron Emission Tomography) Scan
PET scans are used in the diagnosis of brain tumours and lymphoma.
PET scanning is a relatively new technique and is likely to become much more widespread over the next few years. It involves injecting a glucose substance into the blood stream that has been labeled with radioactivity by a machine called a cyclotron. This substance is then able to show tissues that are either under- or over-using glucose. Cancer cells, because they are reproducing and dividing rapidly, use a lot of glucose and these areas can be seen on the scan pictures. Unlike CT and MRI, where there can sometimes be difficulty determining whether the abnormal area seen is cancerous, PET scanning is more accurate. One of the major problems with PET scanning at the present time is its availability. It is not yet available in Pakistan but expected soon at Shaukat Khanum Cancer Hospital. Mostly patients are referred to India or Singapore.
X-rays are probably the simplest and least invasive of the diagnostic and staging investigations. The amount of radioactivity exposure from a bone X-ray is very small compared to, for example, a CT scan. Cancers of the bone have particular characteristics, such as loss of density, which can be recognised on X-ray films. X-rays may also be used to determine whether the bone cancer is a primary cancer or has spread from another cancer that originated elsewhere.
A simple blood test from a peripheral vein may show a high number of white blood cells and also the presence of leukaemia cells. Some tumor markers like Alpha fetoprotein, Beta HCG and LDH can give useful information about specific cancers.
When we talk about staging a cancer we are finding out exactly how advanced the cancer is at the time it has been diagnosed. This process is vital if the patient is to receive the treatment that is most appropriate for them. Accurate staging should:
- Identify those patients who would not benefit from aggressive modes of treatment so that they do not undergo these treatments unnecessarily;
- Identify the group of patients who are likely to benefit from either neo-adjuvant (treatment before the main treatment) or adjuvant therapy (treatment after or alongside the main treatment);
- Provide important information for the research and audit of the particular cancer.
One of the most important aspects of the staging process is to identify those patients who either can or cannot be operated on. Patients that undergo an operation only to find that the cancer is not resectable will have had an operation unnecessarily. This not only has increased mortality and morbidity but also has a detrimental effect on the patient’s quality of life.
There are many different staging systems used to describe how advanced the cancer is. An example of this is the TNM system which is commonly used in order to accurately stage a cancer. This system provides information about the size of the cancer and whether surrounding structures are involved (T factor), the extent of any lymph node involvement (N factor) and also the detection of any distant spread – metastases (M factor). Once the TNM is worked out the stage of disease can be determined. The stage of disease is usually I, II, III or IV.
The higher the stage of disease found on diagnosis, the worse the prognosis is for patients. Those with Stage IV disease (distant metastases present) have the worst prognosis.
Other staging systems are used for diseases such as lymphoma which is staged according to the position and number of lymph nodes.
The actual staging process begins when the patient first presents with symptoms. The process will include taking the history of the patient, clinical examination and basic haematological investigation. This may immediately identify obvious signs of metastatic disease. Further, more specific tests will then be undertaken, for example, MRI or CT scans. The results of the staging investigation will then determine the treatment offered. For example, if a retinoblastoma is diagnosed that is small and localised to the eye it can be treated using either cryotherapy to freeze it or laser therapy to burn it. With larger tumours or those that have spread, it may be necessary to surgically remove the eye and / or use radiotherapy or chemotherapy in an attempt to cure the disease.