Background

This usually solitary keratotic lesion clinically resembles a lentigo, Bowen's disease, or a basal cell carcinoma. It is also known as a benign lichenoid keratosis and involuting lichenoid plaque. It usually occurs on extremities and presternal area, often in sun-exposed areas. As the name suggests, its histology resembles lichen planus though there may be subtle differences. It probably represents a regressing lentigo or seborrheic keratosis and if sought for, a remnant of these former lesions may be found.

The pathologist must differentiate between this lesion and lichen planus. The most helpful clue is the clinical presentation. If multiple lesions are present, lichen planus is the probable diagnosis.

OUTLINE

Histopathological Features and Variants
Commonly Used Terms
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HISTOPATOLOGY	CHARACTERIZATION
Benign lichenoid keratosis: a clinical and pathologic reappraisal of 1040 cases. Morgan MB, Stevens GL, Switlyk S. University of South Florida College of Medicine, Tampa, FL, USA.	Am J Dermatopathol. 2005 Oct;27(5):387-92. Abstract quote   Benign lichenoid keratosis, otherwise known as lichen planus-like keratosis, is a common, cutaneous entity that is often confused with cutaneous malignancy. Few studies have examined the multiple clinical and pathologic guises of this entity, particularly within the context of clinical pathologic correlation or magnitude of this study. We examined the epidemiologic, clinical, and pathologic attributes of 1040 consecutive cases of benign lichenoid keratosis referred for pathologic examination at a busy laboratory over an entire year. Clinical parameters assessed included the age, anatomic location, gender, and multiplicity of the lesions. Pathologic attributes were assessed yielding discernment of five different subtypes that included a classic type, bullous type, atypical type with cytologically atypical lymphocytes, an early or interface type, and a late regressed or atrophic type. The results yielded an average age at presentation of 59.5 years with an age range of 36 to 87 years. The gender frequency was 76% female, 24% male. The trunk was the most common location (76%), followed by the extremities (33%) and head and neck (7%); 8% of patients presented with two lesions and less than 1% with three lesions prompting consideration of lichen planus. The classic, atypical, and bullous forms of the disease clinically presented with erythematous papule/plaque(s). The early or interface type showed erythematous to hyperpigmented brown macules and the regressed or atrophic type presented as violaceous papules or irregularly distributed macular pigmentation; 81% of the lesions showed the classic histology consisting of epidermal acanthosis with a band-like lichenoid lymphocytic infiltrate. Variable numbers of plasma cells, eosinophils, and neutrophils were identified as well as epidermal parakeratosis distinguishing these lesions from typical lichen planus. The bullous variant showed intraepidermal or subepidermal bullous cavities with a dense associated lymphocytic infiltrate and increased numbers of necrotic basilar layer keratinocytes. The atypical variant showed features of the classic type with scattered enlarged CD-3, CD-30 (+) lymphocytes possessing hyperchromatic, irregular nuclei. The early interface type showed single lymphocytes aligned along the dermoepidermal junction without epidermal acanthosis and adjacent lentigo. The regressed or atrophic variant showed epidermal atrophy with papillary dermal scarring, patchy lymphocytic infiltrates and melanin incontinence. The clinicopathologic spectrum of benign lichenoid keratosis is broad and encompasses several unrelated entities. An awareness of its expanded presentation is essential to avoid misdiagnosis and may serve as an important forerunner of pathogenic discernment.
Lichenoid keratosis: a clinicopathologic study of 17 patients. Jang KA, Kim SH, Choi JH, Sung KJ, Moon KC, Koh JK. Department of Dermatology, Asan Medical Center, College of Medicine, University of Ulsan, Seoul, Korea.	J Am Acad Dermatol 2000 Sep;43(3):511-6 Abstract quote BACKGROUND: Lichenoid keratosis (LK) is a rather frequent skin lesion that has some histologic features similar to lichen planus (LP). The clinical and histopathologic characteristics of LK and differential tools from LP are not yet fully established. OBJECTIVE: The purpose of this study was to investigate the clinical and histopathologic characteristics of LK. METHODS: A clinical survey was done with 17 patients diagnosed as having LK. We reevaluated biopsy materials of 17 patients diagnosed during the past 10 years at Asan Medical Center, Seoul, Korea. We performed an immunohistochemical staining in 17 cases of LK and 7 cases of LP using 5 antibodies for CD3, CD4, CD8, CD20, and cutaneous lymphocyte-associated antigen (CLA). Standard streptavidin-biotin peroxidase method using the monoclonal antibodies with 3-amino-9-ethyl-carbazole was used. RESULTS: The male/female ratio was 1:1.1. The mean age at diagnosis was 54.9 years. The face was the most commonly affected site, followed by the arm and forearm, dorsum of hand, chest, trunk, abdomen, and leg. The lesions were predominantly solitary (76.5%); 1 patient had 4 lesions; 3 patients (17.6%) had numerous lesions. The lesions ranged in size from 0.4 to 2.0 cm. Histopathologically, all the cases showed characteristic lichenoid infiltrates of lymphocytes, occasional parakeratosis, and apoptotic bodies in the epidermis without nuclear atypia of keratinocytes. LK could be reclassified into 3 patterns by means of histopathologic findings: LP-like (11/17), seborrheic keratosis-like (3/17), and lupus erythematosus-like (3/17). Immunohistochemical studies revealed that infiltrated epidermal and dermal lymphocytes in LK consisted mainly of CD8(+) T cells and partly CD20(+) B cells. In LP, epidermal lymphocytes were mainly CD8(+) T cells and dermal lymphocytes were CD4(+) or CD8(+) T cells. Interestingly, CLA was strongly expressed in LP but not expressed in LK. CONCLUSION: We reclassified LK as follows: LP-like LK, seborrheic keratosis-like LK, and lupus erythematosus-like LK. Immunohistochemical stains for CLA as well as CD4 and CD8 may be valuable tools in the differential diagnosis between LK and LP.
VARIANTS
Benign lichenoid keratoses with histologic features of mycosis fungoides: clinicopathologic description of a clinically significant histologic pattern. Al-Hoqail IA, Crawford RI. Department of Dermatology, King Khalid University Hospital and Faculty of Medicine at King Saud University, Riyadh, Saudi Arabia, Division of Dermatology and Department of Pathology, University of British Columbia, Vancouver, Canada.	J Cutan Pathol 2002 May;29(5):291-4 Abstract quote Background: Benign lichenoid keratosis (BLK) is a well-known clinicopathologic entity and several histopathologic patterns havebeen described. Features mimicking mycosis fungoides (MF) in clinically typical BLKs have not yet been emphasized. The aim of this study was to confirm the occurrence of an MF-like pattern of BLK. Methods: A retrospective survey was conducted on cases diagnosed as BLK over a 9-month period in a regional dermatopathology service. Seven histologic parameters, previously confirmed as diagnostically suggestive of MF, were applied. Inclusion criteria were: three or more MF-related histologic features and a size less than 2 cm. The clinical features were reviewed. Results: Fifteen cases of MF-pattern BLK were identified. The number of MF-like parameters present in individual cases exceeded the inclusion criteria by variable amounts. Pautrier microabscesses and alignment of lymphocytes along the basal layer were the most frequent (14/15). The age of the patients ranged from 28 to 83 years, with a mean of 50. The size of the lesions ranged from 0.2 to 1.8 cm, with a mean of 0.6 cm. The upper trunk was the favored site. Most of the lesions had been removed because of suspicion of cutaneous malignancy; basal cell carcinoma was the most frequent clinical diagnosis. Conclusion: We describe an MF-like histologic pattern of BLK. Pathologists and dermatopathologists should be aware of this novel histologic pattern to facilitate distinction between the two disorders.

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Keratoses

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Last Updated October 17, 2005

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