Dermoscopy Frequently Asked Questions

What is the difference between epiluminescence microscopy, dermatoscopy and dermoscopy?

There is no difference at all, just different names for the same technique. In 2001 at the 1st World Congress of Dermoscopy the various terms were discussed and it was decided that in order to unify the terminology particularly with respect to research the term "Dermoscopy" should be used.

Why should a dermatologist use dermoscopy?

Dermoscopy is a fusion of the two major principles that facilitate good skin examination, namely magnification and illumination.

By using dermoscopy dermatologists will be forced to examine individual lesions more closely. Their diagnostic accuracy for diagnosing not only pigmented skin lesions and melanoma, but also a whole variety of dermatoses, including infections and inflammatory conditions will increase, with time and training. E.g. the scabies mite will no longer be able to hide!

How should a dermatologist start to use dermoscopy?

As with all aspects of medicine, diagnostic accuracy increases with experience. It takes time and perseverance. We suggest that doctors beginning with dermoscopy should continue to rely on their clinical judgement and should start to use dermoscopy for unequivocal lesions only. In this way their familiarity with dermoscopic features will gradually increase.

Attending a course or meeting in dermoscopy will increase your confidence in dermoscopy and will increase your diagnostic accuracy particularly for pigmented skin lesions in general and early invasive melanoma, including melanoma in-situ. Caution should be employed when starting to use dermoscopy without training as there is evidence that your diagnostic accuracy may reduce.

What are the limits of dermoscopy?

Dermoscopy allows visualization of the horizontal plane of a given skin lesion only to the level of the papillary dermis. Structures in the reticular dermis cannot be seen, just like with the naked eye.

Heavily pigmented skin lesions are sometimes very difficult to diagnose, and hypopigmented or amelanotic melanoma represents a particular diagnostic challenge. Very thick tumours may lack a number of dermoscopic features and thus clinical experience and clinical diagnosis remains very important in these lesions.

If diagnostic doubt remains with dermoscopy then the lesion should be biopsied; dermoscopy is not 100%, so do not expect it to be!

Which dermatoscope is best?

There are 2 main types of dermatoscopes; oil immersion (non-polarised) and cross-polarised.

Oil immersion dermatoscopes (non-polarised) have a longer history of use in dermatology, however the inconvenience of applying an oil or interface fluid (alcohol gel or ultrasound gel) makes these instruments time consuming when multiple lesions are being examined. There is also the potential for cross contamination they involve contact with the patient. They have a bright image and may have a heavy handle although newer devices are more portable and compact.

Cross-polarised light dermatoscopes are becoming very popular with dermoscopy enthusiasts as they are now of a suitable quality that the device brightness is comparable with the oil immersion instruments. They are more expensive, however they are more versatile, smaller and lighter, and multiple lesions can be examined quickly without the need for interface fluid application. Newer devices have an extendable faceplate for use with interface fluid if needed; this can improve the image quality.

Ultimately the choice of dermatoscope will reside with the doctor and include factors such as personal preference, and likely population of patients to be examined. Note, some dermoscopic structures are seen differently with the two types of devices, and it may take some time to get your eye in with the new device. Devices are now available that combine both cross-polarised and oil immersion features.

Both instruments are battery operated therefore do not forget to keep them fully charged!

Hybrid devices

Recently hybrid devices have been developed to combine the clarity of the contact oil immersion device with the practicality of the polarised devices.

The new Dermlite DL3 is a single device that is truely comparable to the market leaders in both polarised and non-polarised dermoscopy. This device will become a very popular instrument with clinicians, with its bright illumination, large field of view and versatility in both polarised and non-polarised modes.

What type of immersion oil is best used for the oil immersion dermatoscopes?

Alcohol gel is preferred, as it should be easy to hand in the examination room and will reduce the theoretical risk of cross contamination. Around the eyes and nails ultrasound gel is beneficial as it will not irritate the eye and does not run off the nail.

For the instruments with cross-polarised lenses there is no need for immersion oil; however care should still be taken to keep the instrument clean and to avoid cross contamination between patients.

Do not forget to clean the instrument with alcohol gel if ultrasound gel was used!

What magnification is the best used for dermoscopy?

A 10-fold magnification is standard for hand held devices.

What camera should I buy to take dermoscopic images?

Both types of hand held dermatoscopes can usually be connected to digital cameras, either directly, via a screw thread, or via adapter rings. Cameras and dermatoscopes vary and may not be compatible, therefore please contact the manufacturer of the device for specific recommendations. The cross-polarised devices need to be placed in contact with skin to avoid camera shake, the newer devices have an extendable faceplate for this purpose. Again consider the risk of cross contamination.

What is the role for computer assisted digital mole mapping?

Research into this field is increasing. At present the computer systems have limitations including being expensive and bulky compared with hand held devices. Their image resolution is inferior to hand held devices and independent research has published limitations in the diagnostic ability of the software in these systems. Finally the software of these systems can only comment on lesions pre-selected for examination.

However, they also have some advantages including the ability to catalogue numerous naevi, thereby facilitating easier follow up of some patients. These images are standardised for magnification and brightness, and are easily compared with earlier images taken with the same device.

Therefore we would not recommend their use for diagnostic purposes alone; however they will play an increasing part of dermatology practice particularly in the follow up of patients with multiple naevi.

10 tips to improve dermoscopic imaging

1. Clean the dermatoscope and camera lenses.
2. Ensure the dermatoscope and camera are both fully charged.
3. Adjust camera to the ?macro? setting.
4. Ensure the dermatoscope is in contact with the skin (extend the foot-plate on the newer Dermlite devices).
5. Use interface medium to reduce surface light scatter and apply carefully to reduce air bubbles.
6. Use ultrasound gel for imaging nails.
7. Remove graticule if focusing on deeper structures is difficult.
8. For larger lesions use a dermatoscope with a large field of view.
9. Adjust horizontal and lateral pressure.
10. Take multiple images and save the best!