Lentigo maligna (LM) is the in situ phase of lentigo maligna melanoma (LMM). A wide variety of modalities has been used to manage LM, including conventional surgery, staged excision, Mohs micrographic surgery, cryotherapy, radiotherapy, laser therapy, and, recently, imiquimod.

Soft x-radiation is an accepted treatment for LM/LMM. The aim of the present study was to evaluate the efficacy and safety of ultra-soft x-ray/grenz-ray (GR) treatment in patients with LM and early LMM.

Five hundred ninety-three patients were treated with GR (primary therapy, n = 350; partial excision followed by GR, n = 71; radical excision followed by GR as recurrence-prophylactic treatment, n = 172) at the Department of Dermatology, Karolinska University Hospital, Stockholm, Sweden between 1990 and 2009. The treatment was given twice a week over 3 consecutive weeks in total doses of 100 to 160 Gy. Dosage depended on the stage of LM and the depth of periadnexal atypical melanocytic extension in histologically examined materials before treatment. Four hundred twenty-five patients have been followed up for at least 2 years; of these, 241 for 5 years.

Overall, 520 of 593 patients (88%) showed complete clearance after one fractionated treatment. Residual lesions were seen in 15 patients, and 58 relapsed, 53 of whom (72%) within 2 years.

Woods light examination was not used in the clinical diagnosis of lentigo maligna.

GR is an efficient and safe treatment in LM and early LMM when administered according to the recommendations presented herein. Moreover, GR offers an excellent cosmetic result.