K. de Vries

Recurrence rate of lentigo maligna after micrographically controlled staged surgical excision

Lentigo maligna is a slowly growing melanoma in situ. Current guidelines advise wide local excision with a margin of 5 mm as the treatment of first choice, which has recurrence rates ranging from 6% to 20%.

Influence of atmospheric electric fields on the radio emission from extensive air showers

The atmospheric electric fields in thunderclouds have been shown to significantly modify the intensity and polarization patterns of the radio footprint of cosmic-ray-induced extensive air showers. ...

Measurement of the circular polarization in radio emission from extensive air showers confirms emission mechanisms

We report here on a novel analysis of the complete set of four Stokes parameters that uniquely determine the linear and/or circular polarization of the radio signal for an extensive air shower. The observed dependency of the circular polarization on azimuth angle and distance to the shower axis is a clear signature of the interfering contributions from two different radiation mechanisms, a main contribution due to a geomagnetically-induced transverse current and a secondary component due to the build-up of excess charge at the shower front. The data, as measured at LOFAR, agree very well with a calculation from first principles. This opens the possibility to use circular polarization as an investigative tool in the analysis of air shower structure, such as for the determination of atmospheric electric fields.

Laser Treatment and Its Implications for Photodamaged Skin and Actinic Keratosis

Treatment of widespread actinic keratoses (AKs) and extensive photodamage is a challenge. One of the treatment options is laser therapy, whereby physicians have the option of using ablative lasers (CO2 and Erbium Yttrium Aluminium Garnet) or nonablative fractional laser systems. With ablative laser systems, the superficial layers of the skin are ablated, including epidermal and superficial dermal actinic damage. Re-epithelialization occurs from uninvolved skin and keratinocytes from follicles. When using a CO2 laser, additional cosmetic improvements are a result of removal and tightening of the photodamaged collagen in the superficial dermis. The most important risks of this treatment are scarring and dyspigmentation. These risks are lessened when using fractional lasers, which produce small columns of ablation or coagulation in the skin, leaving the surrounding skin intact. This treatment may be combined with topical agents. Existing evidence suggests that both ablative laser resurfacing and fractional laser treatments are effective in reducing AKs and photodamage. Although these treatment modalities are widely used and clinical experiences are positive, large comparative studies are remarkably scarce. Still, laser resurfacing has a place in the (field) treatment of widespread AKs and extensive photodamage.

A two-stage treatment of lentigo maligna using ablative laser therapy followed by imiquimod: excellent cosmesis, but frequent recurrences on the nose

DEAR EDITOR, Lentigo maligna is the most common subtype of melanoma in situ, with a rapidly growing incidence. It typically arises in chronically sun-exposed skin of elderly individuals. Estimates of the lifetime risk of lentigo maligna progressing to lentigo maligna melanoma vary from 2 2% to 4 7%. The primary treatment goal is complete eradication of the lesion with prevention of recurrences. Surgical excision is the recommended treatment. As lentigo maligna occurs mainly in the head and neck region, important secondary goals are to minimize functional and cosmetic deformities. In large facial lesions or in elderly patients, alternative nonsurgical treatments, or even a wait-and-see policy, may be considered. Our department has introduced a novel treatment combination of ablative laser therapy followed by 6 weeks of topical imiquimod 5% application. Lentigo maligna lesions were first treated with ablative laser therapy with margins of 2–3 cm of adjacent skin to remove the large bulk of atypical melanocytes. The epidermis and superficial papillary dermis were ablated with either 2940-nm erbium-doped yttrium aluminium garnet laser or 10 600-nm CO2 laser. End points of the laser treatment were complete pigment clearance and visible punctuate bleeding. After laser treatment, patients started daily application of imiquimod 5% cream on the erosive skin for 5 days a week for 6 weeks. This topical Toll-like receptor 7 and 8 agonist induced an inflammatory immune response to clear any residual atypical melanocytes. The degree of inflammation was assessed at regular intervals, and depending on the local inflammatory reaction the frequency was increased to twice daily, or reduced to 3 days a week. Potential flu-like symptoms caused by imiquimod were counteracted by 1 g of paracetamol 1–2 h before and 6–8 h after application of imiquimod cream. In our previous publication we reported the absence of recurrences in 12 patients after a mean follow-up of 22 months, with good-to-excellent cosmetic results. We have now reviewed 35 patients who were treated in a similar fashion and present the recurrence rates and patient satisfaction of this cohort, including the long-term follow-up results of the original cohort. All patients with histologically proven lentigo maligna, who had undergone ablative laser therapy followed by imiquimod, between 2008 and 2014, were retrospectively identified. Data collected included age, sex, anatomical site of the lesion, histopathological results, treatment details (laser device, duration and dosing regimen of imiquimod cream), follow-up