Cockarde (Target-Like Lesion) Seborrheic Keratosis: An Unusual Clinical Pattern

Abstract

Dear Editor: Seborrheic keratosis (SK) is the most common type of benign epidermal neoplasm, and has variable clinical presentation. Typically, SK first presents as yellowish, circumscribed papules, which later become more exophytic, brown and/or hyperpigmented. Greasy, adherent squamous material subsequently develops1. These lesions commonly present as round or oval keratotic papules or plaques with a classically papillomatous surface that is sprinkled with comedon-like openings. To the best of our knowledge, SK with a target-like morphology has not been previously reported. Herein, we report a case of SK with an uncommon target-like appearance, which we denominate 'cockarde (target-like lesion) SK'. A 57-year-old woman presented to our clinic with a several-year history of an asymptomatic lesion on her left thigh, which she reported to have gradually increased in size over the past several months. The patient denied any other relevant clinical past history, and all initial laboratory tests were within normal limits. Dermatologic examination revealed a sharply demarcated, slightly elevated, well-defined, darkly pigmented, target-shaped lesion on the left thigh. Additionally, the lesion contained a round black inner plaque measuring 0.5 cm in diameter, which was surrounded by a light brown arcuate patch, so that the diameter of the overall lesion was 1.5 cm (Fig. 1). Fig. 1 Targetoid seborrheic keratosis. Central black plaque surrounded by a brownish patch. A subsequent elliptical biopsy was performed containing the inner round plaque and a part of the surrounding patch (Asterisk: round black inner plaque. Black and white ... An elliptical biopsy including the inner round plaque and part of the surrounding patch was then performed, with the subsequent histopathological examination revealing generalized hyperkeratosis and acanthosis and a proliferation of sharply demarcated intraepithelial nests of large pale cells in the epidermis of the central lesion. The adjacent epidermis in the specimen was also noted to lie on a straight line. Given these histological features, a diagnosis of SK (clonal type) was reached (Fig. 2). Fig. 2 Histopathologic characteristics of seborrheic keratosis (clonal type). (A, B) Histopathological examination revealed generalized hyperkeratosis, acanthosis, and a proliferation of sharply demarcated intraepithelial nests of large pale cells in the epidermis ... In the dermatology literature, target-like lesions are most commonly associated with erythema multiforme, Stevens-Johnson's syndrome, toxic epidermal necrolysis2, cockarde nevus3, drug eruption, vasculitis, acute hemorrhagic edema of infancy, and various connective tissue and blistering diseases4. Therefore, when a patient complains of a target-like lesion, the above-mentioned diseases should be considered in the first instance. In many cases, SK can be readily diagnosed based on clinical presentation. However, Bryant5 reported that only 44.1% of cases of SK are correctly diagnosed by dermatologists. The report also suggests that SK in which lesions present with an unusual appearance is likely to be even more difficult to diagnose. Although SK is divided into many subtypes, its clinical variants are rare: these have been reported to be stucco keratosis, dermatosis papulosa nigra, and Leser-Trelat syndrome1. To the best of our knowledge, target-like SK or cockarde SK has not previously been reported in the literature. As such, we contend that this case is unique secondary to the presenting clinical features, and thus propose that 'cockarde SK' be recognized as an additional clinical variant of SK. Knowledge of this unusual variant of SK would be helpful in differentiating several target-shaped diseases, as well as in making a proper diagnosis of this rare condition.