Background: Lymphomatoid papulosis (LyP) is a chronic dermatosis that histologically resembles malignant lymphoma. Thus far, only a few cases of LyP have been characterized in detail with regard to immunophenotype, genotype, and karyotype. Objective: Our purpose was to study seven patients with LyP and compare the results to those reported in the literature. Methods: Skin biopsy specimens were analyzed by frozen section immunohistochemical and molecular biologic techniques. Cytogenetic analysis was also performed in three cases. Results: The atypical lymphoid cells consisted of activated helper T cells; four of the seven patients had lesions with a detectable clonal T-cell population. A peripheral T-cell lymphoma developed in one patient before the emergence of a genotypically different LyP T-cell clone. Cytogenetic studies were abnormal in one case of LyP and normal in another, whereas the karyotype of the lymphoma was abnormal. Conclusion: LyP is a preneoplastic proliferation of activated helper T cells, which is often clonal and may regress and expand with the development of new LyP clones or lymphoma.
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