Objective: To provide evidence that lymphomatoid keratosis should be categorized as an epidermotropic subtype of cutaneous lymphoid hyperplasia. Design: Clinicopathological, immunohistochemical, and molecular biological studies of epidermotropic and dermal bandlike infiltrates of lymphocytes without necrotic keratinocytes, Civatte bodies, or Max-Joseph spaces and solar lentigo or seborrheic keratosis adjacent to the lesion, but with epidermal hyperplastic change (clinically scaly plaque) in

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... s of lymphomatoid keratosis. Conventional histopathologic study as well as immunohistochemical examinations for CD1a, CD3, CD4, CD8, CD20, and CD79a and S100 protein and genotypic examinations were performed. Setting: University departments comprising 2 sections of dermatology and 1 section of pathology. Main Outcome Measures: Ratio of T to B cells and of CD4 ϩ to CD8 ϩ cells, and the phenotype of epidermotropic cells were evaluated. Gene rearrangement of the immunoglobulin heavy chain gene and T-cell receptor (TCR)-␤ and TCRγ genes was also investigated by the polymerase chain reaction method. Presence of mononuclear cells in the epidermis without spongiosis occurring in MF. The