Lichenoid keratosis: A clinicopathologic study of 17 patients

Background: Lichenoid keratosis (LK) is a rather frequent skin lesion that has some histologic features similar to lichen planus (LP). The clinical an d 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 hi stopathologic 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 immunohistoc hemical 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). St andard streptavidin-biotin peroxidase method using the monoclonal antibodie s 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 we re 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. Hi stopathologically, all the cases showed characteristic lichenoid infiltrate s of lymphocytes, occasional parakeratosis, and apoptotic bodies in the epi dermis without nuclear atypia of keratinocytes. LK could be reclassified in to 3 patterns by means of histopathologic findings: LP-like (11/17), seborr heic keratosis-like (3/17), and lupus erythematosus-like (3/17). Immunohist ochemical studies revealed that infiltrated epidermal and dermal lymphocyte s in LK consisted mainly of CD8(+) T cells and partly CD20(+) B cells. In L P, 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 C LA as well as CD4 and CD8 may be valuable tools in the differential diagnos is between LK and LP.