Lichen planus-like keratosis of the face: a simulator of melanoma in situ

Clinical and dermoscopic features associated with lichen planus-like keratoses that undergo skin biopsy: A single-center, observational study

BACKGROUND/OBJECTIVES

Lichen planus-like keratoses (LPLK) are benign skin lesions that can mimic malignancy; the clinical and dermoscopic features distinguishing lichen planus-like keratoses from skin tumors have not been extensively studied. The objective of this study was to identify dermoscopic features that may prevent unnecessary biopsies of lichen planus-like keratoses.

METHODS

Retrospective, single-center, observational study of biopsied skin lesions at a tertiary center. We compared 355 lichen planus-like keratoses to 118 non-lichen planus-like keratoses lesions with lichen planus-like keratosis in the differential diagnosis biopsied from August 1, 2015, to December 31, 2016. The investigators were blinded to the diagnosis of the lesions.

RESULTS

Lichen planus-like keratoses were most frequently non-pigmented (61.7%), truncal (52.1%), and on sun-damaged skin (69.6%); the majority occurred in Whites (95.5%) and females (62.8%). Dermoscopically, lichen planus-like keratoses were more likely than non-lichen planus-like keratoses to have scale (42.5% vs 31.4%, P = 0.03) and orange colour (8.2% vs 0.9%, P = 0.01). Among lesions with peppering (n = 76; 63 lichen planus-like keratoses and 13 non-lichen planus-like keratoses), coarse ± fine peppering (73% vs 38.5%, P = 0.02) and peppering as the only feature (34.9% vs 0%, P = 0.01) were associated with lichen planus-like keratoses.

CONCLUSIONS

Lichen planus-like keratoses can be challenging to distinguish from benign and malignant skin tumors. The presence of dermoscopic scale and orange colour may aid in the recognition of lichen planus-like keratosis. Coarse peppering and the presence of peppering as the only dermoscopic feature may further aid the identification of pigmented lichen planus-like keratoses.

Lichen planus-like keratosis: clinical applicability of in vivo reflectance confocal microscopy for an indeterminate cutaneous lesion

Lichen planus-like keratosis (LPLK) is an involuting cutaneous lesion often presenting between the fifth and seventh decades of life. These lesions typically appear abruptly as a solitary macule, papule, or plaque that continuously evolves as it undergoes regression. Clinical and dermoscopic features of LPLK can mimic both benign and malignant lesions, often prompting biopsy for accurate diagnosis. We describe a case of LPLK developing in a patient with a history of multiple skin cancers, including melanoma. Dermoscopy revealed peripheral granules and a central area with pinkish-brown pigmentation and a disorganized pattern with shiny white structures and rosettes. Handheld reflectance confocal microscopy (RCM) showed a typical honeycomb pattern with millia-like cysts and comedo-like openings, and lacked pagetoid and dendritic cells. Based on the benign features seen with RCM, the lesion was followed until complete regression was observed. In conclusion, we describe a case of LPLK with clinically and dermoscopically indeterminate features that was successfully monitored with RCM. We intend to highlight the utility of RCM as a diagnostic aid in equivocal lesions in order to prevent unnecessary excisional procedures.

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.

Extensive regression in pigmented skin lesions: a dangerous confounding feature

Spontaneous regression in melanomas is not an uncommon phenomenon, as it has been described in 10–35% of primary cutaneous lesions [1]. Regression does not appear to predict a more favorable course, since even fully regressed melanomas may progress into metastatic disease [2]. Several dermoscopic features have been correlated with the regression process, including white scar-like depigmented areas and gray-blue, pepper-like granules, which correspond to dermal scarring, pigment incontinence and presence of melanophages [3,4]. Regression may occur not only in melanomas, but also in melanocytic nevi, which similarly may exhibit white areas and gray-blue granules or areas under dermoscopy [5]. Overall, white areas have been proposed to be associated with the fibrosis type of regression and gray-blue areas to the melanosis type of regression of melanocytic tumors [3]. Lichen planus like keratosis (LPLK) is considered to represent a regressed solar lentigo or seborrheic keratosis. Dermoscopy of LPLK at the late stage of the regression process reveals a diffuse gray-blue granular pattern, similar to that observed in regressed melanocytic lesions [6].

In this context, when evaluating skin lesions that exhibit high degree of regression, interpretation of dermoscopic findings may be problematic, especially when no other dermoscopic clues can be recognized.

Reflectance confocal microscopy criteria of lichen planus-like keratosis

BACKGROUND

Lichen planus-like keratosis (LPLK) may be difficult to differentiate from melanoma and other skin cancers on sun-damaged skin based on clinical and dermoscopic examination. Reflectance confocal microscopy (RCM) allows evaluation of skin lesions at high resolution.

OBJECTIVES

The aim of this study was to identify criteria for specific diagnosis of LPLK using in vivo RCM.

METHODS

Lesions included in the study were derived from patients presenting for skin examination at a private dermatology practice specializing in skin cancer. We retrospectively analysed RCM features of 28 biopsy-proven LPLK and compared them to RCM findings in skin cancers on sun-damaged skin, including five in situ squamous cell carcinomas, six actinic keratoses, seven superficial basal cell carcinomas and eight melanomas.

RESULTS

The main RCM features of LPLK and their relative frequencies were: (i) typical honeycomb pattern of the spinous layer (78.6%); (ii) elongated cords and/or bulbous projections at the dermal-epidermal junction (75%); and (iii) numerous plump-bright cells and/or bright stellate spots in the superficial dermis (92.9%). These RCM features correlated with the following histopathological findings respectively: (i) spinous-granular layers without significant atypia of keratinocytes; (ii) elongated, bulbous rete ridges; and (iii) dense infiltration of melanophages and lymphocytes in superficial dermis. We propose diagnostic criteria that classify correctly 71.4% of LPLK, while avoiding misclassification of any of the skin cancers in the present series as LPLK.

CONCLUSIONS

We identified RCM criteria for diagnosis of LPLK that correlate well with histopathological findings and that allow differentiation of LPLK from skin cancer.