Change in lentigo maligna score assessed by in vivo reflectance confocal microscopy after one month of imiquimod treatment for lentigo maligna management.

BACKGROUND Treatment of Lentigo Maligna (LM) is challenging because of the potential functional and esthetic surgical sequelae. Imiquimod has been proposed as an alternative treatment for LM. Reflectance Confocal Microscopy (RCM) is a non-invasive tool used for the diagnosis of LM and margin assessment. OBJECTIVE To compare the overall LM score assessed by RCM before and after one month of imiquimod compared to placebo and to define the immunohistochemical (IHC) profile of responders to imiquimod. METHODS A controlled randomized study was conducted. Patients underwent a RCM examination with calculation of the LM score at baseline and after 1 month of treatment. An IHC analysis of excised tissues was performed. RESULTS Forty patients were included. The 1-month LM score was significantly lower in patients treated with imiquimod compared to those treated with placebo (p <0.001). The significantly different criteria were: non-edged papillae, large round pagetoid cells, atypical cells at the dermoepidermal junction, follicular location of atypical cells. The IHC analysis showed a higher level of Interferon gamma in the resected specimens of patients responding to imiquimod (p = 0.04). LIMITATIONS The sample size was small. CONCLUSION Assessing the LM score by RCM was useful to monitor accurately LM response to imiquimod.