Some lesions are obviously suspicious for melanoma. Perhaps they have typical features of melanoma. Maybe they are obviously different from the normal lesions around them. In such cases, the decision to biopsy may be clear. A skin biopsy is necessary to diagnose skin cancer.
But often, cases are less obvious. For example, you could have multiple atypical moles. It may not be possible to biopsy them all. How should you and your doctor decide which lesions to biopsy?
Non-invasive technologies provide information to help make these decisions. Non-invasive means that the procedure does not disturb the body. Some non-invasive technologies are used for finding skin cancer. Examples include dermatoscopy and total body photography. Emerging technologies include smartphone apps and handheld imaging devices. There are pros and cons to using these technologies.
What non-invasive technologies do dermatologists routinely use?
Dermatoscopy is an example of a non-invasive technology. A dermatoscope is a special magnifying glass with a light source. It helps your doctor to see skin structures that are invisible to the naked eye. This information distinguishes harmful lesions from harmless ones.1
Total body photograph is another non-invasive technology. Your doctor photographs your lesions at each appointment. You and your doctor can compare photographs from one appointment to the next. This helps to identify new or changing lesions.2 Similarly, your doctor may photograph specific lesions to monitor over time.
How do smartphone apps help detect skin cancer?
Smartphone apps exist for dermatologists and patients. One 2015 review showed that there were 229 dermatology apps. There were 41 apps to help patients identify melanoma.3 Some of these apps analyze photos based on algorithms. Other apps send images to remote dermatologists to evaluate. Remote dermatologists work at a central location and they do not actually see patients in person.
The US Food and Drug Administration (FDA) regulates some medical apps.4 The FDA cannot evaluate all of them – there are too many. The FDA prioritizes apps that act like a medical device. An example is a heart monitor that links to a mobile device. Apps that claim to detect melanomas might meet this definition.5 However, apps that pose minimal risk to patients do not need premarket FDA approval.4 These include apps that help users:
- Self-manage their disease without providing treatment advice
- Organize and track health information
- Show or communicate potential medical conditions
Melanoma-detecting smartphone apps may make skin self-examinations easier. They might motivate you to see your doctor. However, the safety and accuracy of the apps are important concerns. Trials show that some apps have a low success rate of identifying true positives. For example, only 11% of biopsy-proven melanomas were identified as “high risk” by one app.3 Other apps were more successful – especially the apps linked with a remote dermatologist.
A user is most likely to analyze lesions that already seem unusual.3 For this reason, an app cannot replace a total body skin exam. A professional exam can identify suspicious lesions that you had not noticed.
Questions to consider before using a skin cancer smartphone app include:
- How does the app work? Is it algorithmic? Does it connect to a remote dermatologist?
- Has the app been tested in an independent clinical trial?
- Out of the total number of actual melanomas, how many did the app correctly identify? (This is also called the sensitivity or true positives.)
- Out of the total number of non-melanomas, how many did the app correctly identify? (This is also called the specificity or true negatives.)
- What percentage of lesions could not be analyzed for technical reasons?
Can my doctor find a melanoma with a handheld imaging device?
“Optical biopsy” is a new way of studying a lesion without taking a tissue sample.2 Different technologies are used to do optical biopsy, including:
- Reflectance confocal microscopy (RCM)
- Multispectral imaging
Reflectance confocal microscopy. RCM is mainly used in research right now.3 The instrument used for RCM is very expensive and large. These factors make it impractical for most dermatologists. RCM uses laser light, which passes into the skin as far as the dermis. The light is reflected back to form a picture. This picture has almost as much detail as a sample studied under a microscope.3,6
Multispectral imaging. Multispectral imaging is done by collecting images at various frequencies. These images produce a picture of the mole or lesion that can be analyzed.3 Handheld scanners with this technology are used in the United States. Examples include MelaFind and MoleMate. One criticism of these devices are that they typically recommend biopsy. On the plus side, they identify a high percentage of melanomas. Unfortunately, this also leads to a high number of unnecessary biopsies. Critics say that these devices are no better than an experienced dermatologist with a dermatoscope.3 These imaging tests may not be covered by insurance.