Chronology of lichen planus-like keratosis features by dermoscopy: a summary of 17 cases

Dermoscopic findings for 17 cases of lichen planus-like keratosis (LPLK) were chronologically evaluated. Three males and 14 females were included in the study and the ages ranged from 43 to 85 years (median 65 years). Three cases were diagnosed based on stereotypical dermoscopic findings, while the other 14 cases were histopathologically diagnosed as LPLK. Dermoscopy photographs were divided into four groups depending on the number of days (D) from the initial visit: 1) D = 0 (initial visit or biopsy day); 2) D = 61 to 180; 3) D = 181 to 270; 4) D = 271 to 360. Dermoscopic findings, described as light brown pseudonetwork, pinkish area, gray pseudonetwork, annular granular structures, and blue-gray fine dots, were evaluated at every visit to the hospital. Initial dermoscopy features included light brown pseudonetworks due to residual solar lentigo and overlapping pinkish areas attributed to lichenoid inflammation. Annular granular structures and gray pseudonetwork appeared to be the main features of the regressing stage; these features seemed to progress to "blue-gray fine dots" in the late regressing stage. Blue-gray dots or globules reflecting melanophages, the hallmark dermoscopic features of LPLK, were believed to resolve in approximately one to two years. Based on the clinical and dermoscopic observations, we have specified five stages of evolution of LPLK, namely 1) pre-existing solar lentigo, 2) early inflammatory stage, 3) early regressing stage, 4) regressing stage, and 5) late regressing stage. The limitations of the study are that this is a small-sized, retrospective, observational study and that ethnicity of participants is limited to Japanese patients with skin phototype III.