Diagnosis is the process of finding the cause of a health problem. The process of diagnosis may seem long and frustrating, but it is important for the doctor to rule out other reasons for a health problem before making a cancer diagnosis. Diagnostic tests for melanoma are usually done when:
- the symptoms of melanoma are present, such as a new spot on the skin or change in a mole, freckle, birthmark or coloured spot
- the doctor suspects melanoma after talking with a person about their health and completing a physical examination
Many of the same tests used to initially diagnose cancer are used to determine the stage (how far the cancer has progressed). In general, doctors don’t need to look for spread or metastases of many low-risk melanomas (less than 1 mm thick). More extensive tests may be done for melanomas more than 1 mm thick. Your doctor may also order other tests to check your general health and to help plan your treatment. Tests may include the following.
|Diagnostic tests||Staging and other tests|
The medical history is a record of present symptoms, risk factors and all the medical events and problems a person has had in the past. The medical history of a person’s family may also help the doctor to diagnose melanoma.
In taking a medical history, the doctor will ask questions about:
- a personal history of
- a family history of
- melanoma or other skin cancer
- other cancers
- signs and symptoms
A skin examination allows the doctor to look for any signs of melanoma. During a physical examination, the doctor may:
- note the size, shape, colour and surface texture of the mole, freckle, birthmark or coloured spot
- ask how long the spot has been present and if it has changed in size or appearance
- ask about any symptoms caused by the spot, such as pain, itching or bleeding
- check the lymph nodes near the area
- examine the whole body for other moles, freckles, birthmarks or spots
In addition to the physical skin examination, the doctor may also use dermoscopy (also known as surface microscopy or epiluminescence microscopy). Dermoscopy is used to examine pigmented or non-pigmented lesions for changes that are not visible to the naked eye.
Before the exam, the lesion may be covered with mineral oil to cut down on some of the light reflection from the skin. This makes the lesion easier to see. The doctor then examines the lesion under magnification using a hand-held microscope, a dermatoscope or computerized digital imaging.
Health Canada has recently approved the Verisante Aura, which is a device that visually scans a mole or lesion to determine if it is cancerous. The Aura device is non-invasive. It uses Raman spectroscopy to analyze chemical reactions in the skin, providing immediate and accurate results. It can be used by health professionals to detect both melanoma and non-melanoma skin cancers. Cancer agencies and dermatologists are being encouraged to use Aura, but family doctors can purchase the device as well. It may not be available at all centres. The device could reduce the number of biopsies performed on lesions that turn out to be benign. It may also reduce wait times for surgery for skin cancer.
During a biopsy, tissues or cells are removed from the body so they can be tested in a laboratory. The pathology report from the laboratory will confirm whether or not cancer cells are present in the sample.
Different methods can be used for a skin biopsy. The type of surgical biopsy done depends on the location and size of the affected area.
- Excisional biopsy is the preferred method of biopsy when a melanoma is suspected. It involves removing the entire lesion plus a small amount of normal tissue surrounding the lesion (1–2 mm margin).
- Incisional biopsy is used when an excisional biopsy is not possible because of the size or location of the lesion. Incisional biopsy involves removing part of the lesion.
The most common place for melanoma to spread is the lymph nodes closest to the melanoma. A lymph node biopsy surgically removes lymph nodes so they can be examined under a microscope to find out if they contain cancer.
During a physical examination, the doctor will examine the lymph nodes to check if they look or feel swollen. When the lymph nodes are large and firm to the touch, the doctor may do a fine needle aspiration (FNA) biopsy to find out if the melanoma has spread to the nearby lymph nodes. If the lymph nodes cannot be felt and the melanoma is thicker than 1 mm, a sentinel lymph node biopsy may be done.
Fine needle aspiration (FNA) biopsy
FNA biopsy may be used to remove some fluid from an enlarged lymph node to check for cancer cells. If cancer cells are present, surgery will be done to remove all the lymph nodes in that area (lymph node dissection).
Surgical or excisional lymph node biopsy
Surgery may be done to remove an enlarged lymph node and check for cancer cells.
Sentinel lymph node biopsy
The sentinel node is the first lymph node in a chain or cluster of lymph nodes that receives fluid from the area around a tumour. Cancer cells will most likely spread to these lymph nodes first. Sentinel lymph node biopsy (SLNB) removes the sentinel lymph node so it can be examined to see if it contains cancer cells. There may be more than one sentinel lymph node, depending on the drainage route of the lymph vessels around the tumour.
SLNB is a staging procedure that may be used for people with melanoma to provide prognostic information. It is most often used for people who have melanoma that is thicker than 1 mm, but who do not have any clinical evidence that cancer has spread to the lymph nodes. For melanomas that are less than 1 mm thick, it is unknown whether SLNB can help determine prognosis. It is not known if there is any increased survival benefit after SLNB.
SLNB is not used for people who have:
- melanoma in situ
- stage 1A melanoma
- lymph nodes that the doctor can feel
- already had surgery on a lymph node
- locally advanced melanoma that has spread to the lymph nodes
- metastatic melanoma
SLNB should be done at the same time as surgery to remove melanoma. Preferably, SLNB is done just before surgical removal of melanoma so that it can provide more accurate staging and prognosis information to ensure the melanoma is treated adequately. SLNB can be performed after surgical treatment, in certain cases, but it is preferable to do it at the same time.
If the results of the SLNB are negative (no cancer cells are present), then it is unlikely that other lymph nodes are affected and no additional surgery is necessary. If the results of the SLNB are positive (cancer cells are present), all of the lymph nodes in the area may be removed.
Lymph node dissection
A lymph node dissection involves removing all of the lymph nodes within the anatomic area around the tumour (axilla, groin, or head and neck). This surgery will be done if:
- a FNA or lymph node biopsy shows that melanoma has metastasized to the lymph nodes
- a computed tomography (CT) scan of the head, chest and pelvis shows no obvious metastatic disease
Ultrasound uses high-frequency sound waves to make images of structures in the body. It may be used to monitor or check the lymph nodes.
An x-ray uses small doses of radiation to make an image of the body’s structures on film. A chest x-ray may be used to see if melanoma has spread to the lungs.
A CT scan uses special x-ray equipment to make 3-dimensional and cross-sectional images of organs, tissues, bones and blood vessels inside the body. A computer turns the images into detailed pictures. A CT scan may be used to see if melanoma has spread to the lymph nodes, chest, lungs, liver or brain.
Blood chemistry tests measure certain chemicals in the blood. They show how well certain organs are functioning and can also be used to detect abnormalities. They are used to stage melanoma. Increased lactate dehydrogenase (LDH) indicates a worse prognosis if the cancer has spread (metastasized) to distant sites.
MRI uses powerful magnetic forces and radio-frequency waves to make cross-sectional images of organs, tissues, bones and blood vessels. A computer turns the images into 3-dimensional pictures. It may be used to see if melanoma has spread to the brain and spinal cord.
A PET scan uses radioactive materials (radiopharmaceuticals) to detect changes in the metabolic activity of body tissues. A computer analyzes the radioactive patterns and makes 3-dimensional colour images of the area being scanned. It may be used to see if melanoma has spread to the lymph nodes or has spread to other organs.