Dermoscopy and Ultraviolet Reflectance Dermoscopy of Benign Lichenoid Keratosis Masquerading as Melanoma

Abstract

Benign lichenoid keratosis (BLK), also known as lichen planus-like keratosis, is a benign cutaneous lesion of unknown etiology with overlapping clinical and dermoscopic features with malignant lesions. A 52-year-old female presented with a 10- years history of a single asymptomatic lesion on the left gluteal region not associated with loss of weight, loss of appetite, or other systemic symptoms. Clinical examination revealed a single well-defined violaceous to hyperpigmented plaque of approximately 4 cm × 3 cm in size, on the lateral aspect of the left gluteal region. Dermoscopic examination showed overlapping features of BLK and melanoma. Ultraviolet (UV)dermoscopy showed ‘dermoscopic UV blink sign’ and areas of blue, yellowish-green, and red fluorescence. Histopathological examination showed features suggestive of BLK with no cellular atypia. The patient was started on 5% imiquimod cream 5 days a week and advised to follow up. This case emphasizes the importance of clinical, dermoscopic, UV reflectance dermoscopic, and histopathological correlation in establishing the diagnosis of BLK masquerading as melanoma with regression, thus aiding in the avoidance of unnecessary surgeries.

Introduction

Benign lichenoid keratosis (BLK), also known as lichen planus-like keratosis, solitary lichen planus, involuting lichenoid plaque, and “forme fruste” of lichen planus (LP), is a benign cutaneous lesion of unknown etiology.[1] Despite its benign nature, the overlapping clinical and dermoscopic features with malignant lesions lead to unwanted biopsies and patient anxiety. This case emphasizes the importance of clinical, dermoscopic, ultraviolet (UV) reflectance dermoscopic, and histopathological correlation in clinching the diagnosis of BLK masquerading as melanoma with regression.

Case Report

A 52-year-old female presented with a 10 years history of a single asymptomatic lesion on the left gluteal region, with a recent onset of pain, not associated with pruritus or an increase in the size of the lesion. There was no history of loss of appetite, loss of weight, or any systemic complaints. Clinical examination revealed a single well-defined violaceous to hyperpigmented plaque with a few erythematous areas of approximately 4 cm × 3 cm in size, on the lateral aspect of the left gluteal region [Figure 1]. Based on the clinical features, differential diagnoses of Bowen’s disease, BLK, malignant melanoma, and basal cell carcinoma (BCC) were considered.

Figure 1.

Well-defined violaceous to hyperpigmented plaque with a few erythematous areas of approximately 4 cm × 3 cm in size, on the lateral aspect of the left gluteal region

Dermoscopic examination (Dermlite DL 5, polarised mode, 10× magnification) showed a few comedo-like openings, bluish-white lines in a reticular pattern (suggestive of Wickham striae), multiple structureless blue-gray areas, homogeneous hyperpigmentation in one pole and peripheral brown dots in another pole, blue-white veil pattern, and areas of regression [Figure 2a]. The dermoscopic features in this case showed an overlap of papulo-keratotic and nodular types of BLK. Ultraviolet dermoscopic examination (polarized mode, Dermlite DL5, 10× magnification) showed ‘dermoscopic UV blink sign’ and areas of blue, yellowish-green, and red fluorescence [Figure 2b].

Figure 2.

(a) Dermoscopic examination (Dermlite DL5, polarized mode, 10×) showing a few comedo-like openings (white arrow), Wickham striae (blue arrow), structureless blue-gray areas (green asterisk), homogeneous hyperpigmentation (white asterisk), peripheral brown dots (red arrow), blue-white veil pattern (orange arrow), and areas of regression (yellow asterisk). (b) Ultraviolet reflectance dermoscopic examination showing comedo-like openings (white arrow) and areas of blue, yellowish-green, and red fluorescence

Histopathological examination of incisional skin biopsy showed irregular elongation of rete ridges, fused at places, with band-like lymphocytic infiltrates at the dermo-epidermal junction, occasional Civatte bodies, and perivascular lymphocytic infiltration suggestive of BLK. No features suggestive of dysplasia/atypia were seen [Figure 3]. The patient was started on 5% imiquimod cream 5 days a week and advised to follow up.

Figure 3.

Histopathological examination showing irregular elongation of rete ridges, fused at places, with band-like lymphocytic infiltrates at the dermo-epidermal junction, occasional Civatte bodies, and perivascular lymphocytic infiltration suggestive of BLK (H and E stain, 40x)

Discussion

BLK was first described by Shapiro and Ackerman in 1966 as lichen planus-like keratosis (LPLK).[2] The etiology of BLK is not completely understood. It is thought to result from an immunologically mediated regression of precursor skin lesions such as solar lentigo and seborrheic keratosis.[1] However, studies with histological re-evaluation have failed to establish such a correlation.[3] Epidermotropism of CD1a, CD3, CD8, and CD68-positive inflammatory cells are observed in BLK with cytotoxic T-cells playing a pivotal role in regression.[4]

It typically presents as a solitary lesion on the sun-exposed areas such as the face, upper extremities, and presternal region, with the head and neck being the most common areas involved in the Asian population. It usually occurs in fair-skinned women between the 5^th and 7^th decades of life; however, a recent study has found an equal prevalence among males and females.[1,5] The six clinical types of BLK are flat erythematous, plaque-like, papulo-keratotic, nodular, flat pigmented, and morpheaform, with the most common type being flat erythematous.[6] The other rare variants include bullous, atrophic, and mycosis fungoides like.[5] In lesions that have undergone near-complete regression, the clear diagnosis of prior epithelial or melanocytic lesions becomes difficult.[3]

Morgans and Stevens have described five histopathological variants of BLK.[7] The findings of the classical form include parakeratosis, spongiosis, exocytosis of lymphoid cells, and dermal plasma cell infiltrates. The other histopathological types include atrophic form, bullous form, interface form, and atypical form with atypical lymphocytes within the lichenoid infiltrate.[7] BLK progresses through different phases of evolution or regression. Initially, the lichenoid inflammatory process is accompanied by mild basal cell vacuolar degeneration and dyskeratotic keratinocytes. Over time, the basal cell vacuolization becomes extensive, leading to subepidermal clefting, dyskeratotic keratinocytes in the papillary dermis, and pigment within the dermal macrophages. The periphery of the latter lesions shows changes of regression with an increase in dermal vessels, mild papillary dermal edema, and residual scant inflammatory infiltrate.[4]

The differential diagnoses include lichen planus, BCC, seborrheic keratosis, benign melanocytic lesions, actinic keratosis, sarcoidosis, lupus vulgaris, granuloma annulare, and Bowen’s disease with the most mistaken diagnosis being BCC (52.9%).[1,6] A study by Gori et al.[6] found that 98.1% of BLKs are often misdiagnosed both clinically and pathologically and are usually biopsied to rule out skin cancer. The dermoscopic features of differentials of BLK are explained in Table 1.[6,8]

Table 1.

Dermoscopic findings of differentials of BLK

Benign lichenoid keratosis	Bowen’s disease	Malignant melanoma	Basal cell carcinoma
Cerebriform appearance, comedo-like openings, dotted vessels, telangiectasia, bluish-gray granules, spoke-wheel areas, milky red-white areas, eccentric hyperpigmentation, white scar-like areas, blue ovoid nests	White to yellow surface scales, dotted and/or glomerular vessels, and brown globules on a red-yellowish background	Atypical pigment network, irregular brownish-black dots/globules, bluish-white veil, parallel ridge pattern, and pigment spill	Blue-gray ovoid nests, blue-gray globules, arborizing vessels, telangiectasia, maple leaf-like structures, shiny white-red structureless areas, and white streaks

The clinical and dermoscopic patterns of various clinical types of BLK are explained in Table 2.[6] The main pitfall in diagnosing BLK is the absence of classical dermoscopic features. The dermoscopic features like atypical vessels, telangiectasia, blue-gray granules, eccentric pigmentation, blue ovoid nests, and white scar-like areas overlap with epithelial and melanocyte neoplasms. However, the non-arboriform pattern of telangiectasia, and the coarse nature of gray-blue peppering in BLK help to differentiate it from BCC and melanoma.[6] Studies in the literature do not mention Wickham striae as a dermoscopic feature in BLK, but we observed it in this index case. The common dermoscopic features of BLK and its histopathological correlates are explained in Table 3.[9,10]

Table 2.

Clinical and dermoscopic features of various types of BLK

Characteristics	Flat Pigmented type	Flat Erythematous type	Plaque type	Morphea-form type	Papulo-keratotic type	Nodular type
Prevalence	27.4%	23.5%	13.7%	13.7%	11.9%	9.8%
Clinical presentation	Flat, brownish lesions	Flat, pink-brownish lesions	Slightly raised, pink-brownish lesions, with scaling and ulceration	Slightly depressed, whitish-pink lesions	Slightly raised, pink, or blackish-brown lesions, with scaling	Raised, pink-brownish lesions
Size	<10 mm	10 to 18 mm	<10 mm	<10 mm	<10 mm	<5 mm
Dermoscopy	Linear and dotted vascular structures, telangiectasia, and bluish-gray granules (peppering)	Linear and dotted vascular structures, structures with a cerebriform appearance, milky red-white areas, and gray granules	Comedo-like openings, spoke wheel areas, short pigmented lines, and localized coarse brownish granular pattern	Telangiectasia and short pigmented lines	Brown globules, comedo-like openings, cerebriform pattern, short pigmented lines, and eccentric or central hyperpigmentation	Comedo-like openings, blue-ovoid nests, and white scar-like areas suggestive of regression

Table 3.

Common dermoscopic features of BLK and its histological correlates

Dermoscopic finding	Histological correlate
Telangiectasia	Angiogenesis
Bluish-gray granules	Due to intracellular or extracellular melanin deposition in the mid-deep dermis producing the Tyndall effect
Eccentric/central pigmentation	Pigmentation of basal layer/rete ridges as a result of three-dimensional epidermis viewed in two dimensions
White scar-like areas	Correspond to zones devoid of melanin in the epidermis with associated fibroplasia
Comedo-like openings	Epidermal horn cysts

Immunohistochemical studies also have revealed that BLK, lichenoid actinic keratosis and lichen planus are different entities, and the lymphocyte involvement in the pathogenesis of these lesions also seems to be different. Hence, it is worth considering BLK as a separate entity rather than a mere end-stage regression of pre-existing epithelial or melanocytic lesions.[3]

UV dermoscopic findings of BLK are not available in the literature. However, the prominence of comedo-like openings and milia-like cysts under UV mode has been described, as observed in this case, with a blinking effect when toggled between UV and non-UV modes.[11] The blue fluorescence observed can be attributed to the hyperkeratosis, yellowish-green fluorescence to sweat and bacterial products, and red fluorescence to Cutibacterium acnes.[11,12,13] UV dermoscopy, in addition to dermoscopy, aids in ruling out the mimickers noninvasively and avoiding unnecessary wide local excision.[3,14] The treatment options include topical steroids, 5-fluorouracil cream, 5% imiquimod cream, cryosurgery, electrosurgery, and curettage.[15]

Conclusion

Non-invasive tools like dermoscopy and UV dermoscopy aid in reducing unnecessary surgeries and associated costs for patients by providing clearer diagnostic insights. In patients with suspected malignancies like melanoma, when dermoscopy and UV dermoscopy findings are suggestive of BLK, incision biopsies can be considered as an initial less invasive alternative before proceeding to wide local excision. The observation of unreported dermoscopic and UV dermoscopic features in this case report can help in aiding further research into this entity.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initials will not be published and due efforts will be made to conceal her identity, but anonymity cannot be guaranteed.

Conflicts of interest

There are no conflicts of interest.

Use of artificial intelligence (AI)

The preparation of this manuscript was carried out entirely by the author without the use of artificial intelligence technologies.

Funding Statement

Nil.