Chromosomal rearrangements of 6p25.3 define a new subtype of lymphomatoid papulosis.

Lymphomatoid papulosis (LyP) is an indolent cutaneous lymphoproliferative disorder with clinical and pathologic features overlapping those of both reactive conditions and aggressive lymphomas. Recurrent genetic abnormalities in LyP have not been previously identified. Here, we describe the clinical, immunophenotypic, and genetic characteristics of cutaneous lymphoproliferative lesions showing distinctive and previously undescribed histologic features in 11 patients. All patients were older adults (67 to 88 y) with predominantly localized lesions and clinical presentations suggesting benign inflammatory dermatoses or low-grade epithelial tumors. Histologically, lesions showed a biphasic growth pattern, with small cerebriform lymphocytes in the epidermis and larger transformed lymphocytes in the dermis. All had a T-cell immunophenotype. The pathologic features raised the possibility of an aggressive T-cell lymphoma such as transformed mycosis fungoides. However, no patient developed disseminated skin disease or extracutaneous spread. Untreated lesions regressed spontaneously. All cases harbored chromosomal rearrangements of the DUSP22-IRF4 locus on 6p25.3. The overall findings suggest that these cases represent a newly recognized LyP subtype characterized by 6p25.3 rearrangements. The benign clinical course in all 11 patients despite pathologic features mimicking an aggressive lymphoma emphasizes the importance of clinicopathologic correlation, incorporating molecular genetic analysis when possible, during the evaluation of cutaneous lymphoproliferative disorders.