Aesthetic nurse prescriber Mary White discusses her methods of successfully treating seborrhoeic keratosis with long pulsed alexandrite lasers
I have noticed that patients complaining about seborrhoeic keratoses and requesting removal are becoming more frequent in aesthetic and laser clinics today. I believe this is due to more historic sun damage. Years ago, being tanned was considered to be a sign of ‘lower class’ as it meant you were an outside/manual worker. During the 60s and 70s, celebrities like Coco Chanel made foreign travel and suntans popular, and people started to consider that being tanned was now a desirable feature. I believe we are now seeing the damage that was done decades ago, when sun protection was not widely used. Whilst seborrhoeic keratoses can occur in areas of the body that have not been exposed to sun damage, they are more commonly seen in patients who have a long history of sun exposure, and are less common in patients with Fitzpatrick skin types IV-VI.1
Seborrhoeic keratoses are sometimes referred to as basal cell papillomas, seborrhoeic warts, or senile warts, which are all misnomers as their etiology is not from the wart virus, human papillomavirus (HPV) 2,3 and they are becoming far more prevalent in younger generations. For example, a study of a British population found that seborrhoeic keratoses were present in people younger than 40 years (males, 8.3% and females, 16.7%).2 Seborrhoeic keratoses are warty in appearance, which aids their diagnosis in clinic. Usually raised and sometimes crusty and proliferated, they are similar to a scab or wart/verruca, and their colour varies from very light tan to dark brown and sometimes almost black. They are usually round or oval and symmetrical and can vary in size and diameter with some larger ones growing to more than 2cm wide.4 Seborrhoeic keratosis is a build up of keratinocytes (ordinary skin cells). In the UK by the age of 40, 30% of the population is affected by seborrhoeic keratosis, while by the age of 70 this number increases to 75%. They are not infectious and do not become malignant.7 The diagnosis of seborrhoeic keratoses must not be confused with anything more sinister. Whilst they are classed as benign skin tumours, they can also be present in association with other skin conditions, typically basal cell carcinoma.6 The differential diagnosis is melanoma, although they are not related to melanoma, and this must not be excluded at consultation and diagnosis. The gold standard of diagnosis is achieved following a biopsy of the lesion.6
As the lesions are not cancerous and cause no symptoms, there is no immediate need for treatment or removal. However, most people dislike them as they can be unsightly, can itch, catch on jewellery and bleed if scratched or knocked.
Historically seborrhoeic keratoses were treated using several methods, including: 8
These methods successfully remove the lesions, but are no longer funded on the NHS as they are considered to be cosmetic and usually cause some form of scarring or hypopigmentation.8 The advent of advances in technology with medical lasers means treating seborrhoeic keratoses is now commonplace in many aesthetic and laser clinics. Lasers are useful in treating this condition because the principle of selective photothermolysis makes the incidence of scarring less likely with lasers, as opposed to the other methods, which are non selective and work by ablation.
All lasers have unique characteristics, which determine the outcome of treatment, what condition a specific laser can effectively treat, and how the laser light interacts with the target and influences the clinical outcome. Most lasers that can effectively treat seborrhoeic keratoses fall into the visible range (range that is possible to see with the human eye) of the electromagnetic spectrum, as they are epidermal lesions. Lasers in the visible range that are used to treat these lesions include pulsed dye lasers, long pulsed alexandrite, Argon, KTP and Q-switched ruby.
Other lasers that can be used are erbium:YAG (Er:YAG) and carbon dioxide (CO2). These are not in the visible range but are infrared (IR). Er:YAG is near IR and CO2 is far IR. Near IR means it has a lower wavelength to the visible spectrum, such as 750-900nm. Far IR means it is further away from the visible spectrum, such as 1000-1400nm. They are ablative lasers that vapourise tissue and are useful for destructive therapy of many dermatological lesions.9
When lasers are used in dermatology, it is on the theory of selective photothermolysis, which states that in order to destroy a selected target, while sparing the surrounding tissue, three basic parameters are necessary.10 First of all, the colour of laser light (wavelength) chosen must be one that is absorbed by the target and poorly absorbed by the surrounding tissue. This spares the surrounding tissue from being damaged at the same time by the laser. Secondly, the length of time that the laser beam interacts with the target, that is the pulse duration, must be long enough to destroy the target and is determined by the size of the target. And finally, in order to destroy or alter the target, it must be heated to a high enough temperature to cause permanent damage to that target. Therefore, enough energy must be applied and absorbed for an effective temperature rise.10
Unless you are using the IR lasers for ablation and vapourising, the chromophore (target) for treatment is melanin. Melanin is well absorbed by wavelengths in the visible range of the electromagnetic spectrum.10 Care must be taken when using laser that the competing chromophore of melanin in the surrounding ‘normal’ tissue is unaffected.
Another influencing factor when choosing a laser to treat seborrhoeic keratoses is the depth of penetration of the laser into tissue. This is dependent upon the wavelength of the laser and also the spot size, with larger spot sizes penetrating deeper than smaller ones.10 As seborrhoeic keratoses are epidermal lesions, the clinical endpoint of treatment is the destruction of the lesion. A spot size must be selected that does not penetrate too deeply into tissue, but also must be large enough to make the treatment practical, as some of the lesions can grow to be large.4
Different lasers have different pulse durations. Pulse duration is the amount of time over which the laser pulse is delivered into the chromophore, in this case the melanin in the epidermis. In order for laser treatment to be effective, the pulse duration must be selected in consideration with the thermal relaxation time (TRT) of the chromophore. The pulse duration must be shorter than the TRT of melanin, but not too short that it causes unwanted side effects, such as hyper/hypo pigmentation or even scarring from ablation.10 If the pulse duration is longer than the TRT of melanin, then the target chromophore is not damaged and the energy simply dissipates into the surrounding tissues causing damage there instead.10
The laser in my clinic that is used for the destructive treatment of seborrhoeic keratoses is the long pulsed alexandrite laser by Syneron Candela, which operates at a wavelength of 755 nm and is just in the visible IR part of the spectrum. There are other lasers available such as those manufactured by Lynton Lasers and Cynosure, however I do not have experience using these devices. I have chosen to use an alexandrite laser because it is the latest technology available, the older lasers, such as Argon lasers, have a different wavelength and carry more unwanted side effects such as scarring and hypopigmentation.11 The laser I use delivers a burst of energy using long pulse durations in the remit of milliseconds. Using longer pulse durations delivers the energy in a more controlled and gentle manner than very short durations, such as the acoustic type nanosecond pulse durations delivered with Q-switched lasers.9 Alexandrite laser at 755 nm is delivered into the skin to target melanin lying in the epidermis. When using long pulsed alexandrite laser for treatments such as hair removal, it is vital to protect the epidermis against heat damage by cooling the area either during or immediately before treatment. When treating epidermal lesions such as seborrhoeic keratoses, the target chromophore is the epidermal melanin that needs to be destroyed. We therefore do not pre-cool the skin when using the laser for this particular treatment, as protecting the epidermis by cooling would mean the target is not destroyed. Energy from the laser is absorbed by the epidermal melanin and causes damage to the lesion, which is visible by darkening of the lesion, often with an immediate white eschar. The lesion forms a thickened crust, which flakes off in around 10-14 days. The excess pigment falls away as part of the damaged crust.
My personal experience is that usually one treatment session is enough for most seborrhoeic keratoses, but as the treatment is reliant on absorption into melanin, the lesions that respond best are the ones containing more target chromophore – the darker ones.10 Through my experience treating patients, I have noticed that lighter lesions may respond to higher fluences, but may take more than one treatment session. Repeat sessions should be spaced at eight week intervals because it can take around two to three weeks for the lesion to heal and it is important to wait for the surrounding tissues to settle completely before retreating. The treatment sensation is hot and the skin may be cooled afterwards manually, either by icing, cool air or the application of aloe vera gel. With long pulsed alexandrite laser therapy, the lesions are immediately more visible than before treatment. It is important to explain this thoroughly to the patient at consultation, as it will have social implications.
Normal sequelae of treatment includes immediate darkening (sometimes to almost black), crusting and oedema. From my own observations, these immediate side effects usually disappear after 24-48 hours, but the crusting and scabs will last up to 10-14 days. It is important to let the patient know that picking the scab may cause atrophic scarring – similar to picking chicken pox lesions.
In experienced hands, laser therapy is usually safe and effective for the destructive removal of most seborrhoeic keratoses. However, complications do sometimes occur, and the risk of scarring is generally from poor healing of the tissues after treatment, rather than from the laser treatment itself. Practitioners should be aware that there is a slight risk of permanent hypopigmentation in darker skin types, or those people who are tanned.9 The only other small risk is infection post treatment, which can be managed with oral antibiotics if necessary. After treatment, the risk of the seborrhoeic karatoses reoccurring is slim and rare, but the patient is likely to develop new ones as they are due to historical sun damage.
Seborrhoeic keratoses can be safely and effectively removed using alexandrite laser therapy. The treatment is cost-effective as it usually takes just one session to clear most lesions. The cosmetic perception of improvement after treatment is high – whilst some permanent hypopigmentaton may remain in certain patients, it is my experience that they dislike the rough, crusty feel of the lesions more than the lesion itself. The smooth, flat result is the desired clinical outcome for most people, even if some slight pigmentary changes remain.
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