Early diagnosis of melanoma is essential to enable detection and removal of the abnormal growth before it can progress to a more advanced stage of disease that is more difficult to treat.
As signs of melanoma are usually visible on the skin, visual inspection of the affected area is the most common diagnostic technique used in practice. The ABCDE method is often used to help in the diagnosis of melanoma and includes the following signs:
- Asymmetry: uneven shape of mole or birthmark
- Border: irregular or blurred edge of mole or birthmark
- Color: various color shades or patches of mole or birthmark
- Diameter: spot larger than 6mm (or ¼ inch) in diameter
- Evolving: changes evident in size, shape or color
However, presenting melanomas are not always identical, and it is difficult to clarify melanoma from normal spots on the skin with a simple method. For example, many melanomas may be less than 6 mm in size and many normal moles may, in fact, be larger.
The key point to consider when making a diagnosis of melanoma is change. It can be useful to perform regular examinations with photographic imaging to enable practitioners to establish changes in the shape, size and color of any moles on the skin. It is also helpful to examine all moles, including those smaller in size, to help establish familial patterns that make it easier to recognize when abnormal growth occurs.
The “ugly duckling” sign is a relatively new method that involves identifying moles at risk of melanoma as the look different from other moles on the body. This is a crude, preliminary technique that helps to identify if further investigation is required.
The “little red riding hood” sign is an indicator for patients with fair skin and light-colored hair that are likely to suffer from amelanotic melanomas, which can be difficult to see and, therefore, diagnose. For these individuals, greater care in the screening and diagnostic process is required to ensure that evidence of these melanomas is not missed. A dermatoscope is often used in these patients to detect melanoma that may not appear to be abnormal at an eye’s glance.
Biopsy and Laboratory Testing
If melanoma is suspected following visual examination of the skin, a skin biopsy of the suspicious mole may be taken. Local anesthetic is often used to assist in the process and, in some cases, the entire mole may be removed with the initial biopsy, followed by laboratory testing to confirm the involvement of abnormal cell growth.
Lactate dehydrogenase (LDH) tests can help in the diagnosis of melanoma, although not all patients with the disease will exhibit high levels.
In some cases, patients may require specialized imaging techniques, such as an X-ray, computed tomography (CT) magnetic resonance imaging (MRI) or PET scan.
Patients with melanoma are classified according to the stage of the disease, which helps to make clinical decisions regarding the treatment and to estimate prognosis at five years after diagnosis. .
- Stage 0: Melanoma in situ (99.9% survival)
- Stage I: Invasive melanoma, 1-2 mm in size (89-95% survival)
- Stage II: High-risk melanoma, 2-4 mm in size (45-79% survival)
- Stage III: Regional metastases affect lymph nodes (24-70% survival)
- Stage IV: Distant metastases affect other organs such as lungs or skin (7-19% survival)