Background: Parapsoriasis en plaques (large-plaque type) is a premalignant condition capable of developing into cutaneous T-cell lymphoma (CTCL). However, it is not known whether the early stage of CTCL can be distinguished from parapsoriasis en plaques.
Objective: Our purpose was to determine whether parapsoriasis en plaques can develop into CTCL.
Methods: The clinical appearance, histopathologic features, immunophenotype, DNA rearrangements, and clinical course were analyzed in 20 cases.
Results: T-cell receptor beta-chain gene rearrangement was detected in four of the 20 cases. No clinical, histopathologic, or immunohistochemical differences were found between patients with and without gene rearrangement.
Conclusion: The early stage of CTCL cannot be differentiated from parapsoriasis en plaques by clinical features, histopathologic characteristics, or immunophenotype. Patients with parapsoriasis en plaques exhibit heterogeneous findings, which may include monoclonal proliferation. Patients with long-standing parapsoriasis-like lesions resistant to conventional treatment require careful monitoring for the possible development of cutaneous lymphoma.