Dermoscopy of lichen planus-like keratosis: a model of inflammatory regression

Lichen planus-like keratosis (LPLK) or benign lichenoid keratosis is an involuting cutaneous entity where regressing features are the histologic hallmark. Most authors consider LPLK as an heterogeneous spectrum of intraepithelial epidermal or melanocytic lesions, mainly pigmented, involuting by inflammatory regression.

The authors review the clinico-histologic definition and correlate with the dermoscopic features of LPLK.

Sixteen LPLK were clinically distributed into three types: plaque-like (PL), flat erythematous (FE) and flat pigmented (FP) type and evaluated with conventional dermoscopy. Dermoscopic features of regression were recorded as the presence of blue-white structures and vascular structures. The predominant distribution, size and colour of pigmented granules were also recorded. All cases were excised and submitted to histopathologic examination and subdivided into three groups according to the early, classic and atrophic subtypes.

The FP (44%) and the FE (37%) types are diagnosed more frequently than the PL type (19%). PL type correlates better with the classic type. FE correlates mainly with early/atrophic types, while the FP nearly exclusively with the late atrophic type. Regressive features are present in all but one case with a predominance of blue areas (94%). Localized (55%) and diffuse (37.5%) granular pattern are presenting in all but one case. The diffuse granular pattern correlates with the FP type (5/6 cases), while the localized granular pattern is mainly present (6/9 cases) in the FE type. Vascular structures can be found in half of the cases and white scar-like depigmentation is just present in four cases. BWS and vascular structures present together are observed in four cases (25%).

Our results show a large correlation among clinical, histologic and dermoscopic aspects of LPLK may be interpreted as a spectrum of cutaneous lesions going into inflammatory regression, showing different clinical and dermoscopic patterns according to the involuting stage. The early type of LPLK (FE) shows a localized granular pattern where regression is at the very early stage. The classic dermoscopic features of regressing lesion for LPLK (pigmented granular pattern) apply to the most frequent encountered pigmented atrophic flat type or classic pigmented type, where sometimes regression is advanced or almost complete and no clear diagnosis of a previous benign/malignant - epithelial or melanocytic lesion can often be given. Regressive dermoscopic features must be evaluated in the context of global and clinical pattern of the lesion. Nonetheless dermoscopy can close correlate with clinical incipient or complete regression and must prompt the need for eventual prophylactic surgical removal.