Lichen planus-like keratosis. A clinical and histological reexamination.

Lichen planus-like keratosis (LPLK) is a common skin lesion that has some morphologic features of lichen planus (LP) and lichenoid actinic keratosis (LAK). Although most authors consider LPLK to be a distinct lesion, surgical pathologists are often unfamiliar with it. We examined in detail the clinical and histologic features of LPLK in 100 consecutive cases. In our series, LPLK lesions occurred mostly in late-middle-aged individuals, on the trunk (64%) and extremities (31%) and predominantly in women (73%). Among the 14 histologic parameters that were studied, most LPLK had hyperkeratosis (81%) with hypergranulosis (77%), focal acanthosis (75%), and focal parakeratosis (59%). Solar elastosis was observed in 48% of the cases. Only a few cases had eosinophils (15%) or plasma cells (7%) in the inflammatory infiltrate. The adjacent skin was available for study in 71% of the specimens, and only 26.8% of the cases had an adjacent lesion, most frequently seborrheic keratosis (8.4%), solar lentigo (7%), and actinic keratosis (5.6%). According to our results, the most consistent features observed in LPLK are a lichenoid lymphocytic infiltrate with hyperkeratosis, hypergranulosis, focal acanthosis, and focal parakeratosis, without prominent atypia of keratinocytes.