Cutaneous lymphoid hyperplasias.

Benign hyperplastic lymphoid infiltrates of the skin (pseudolymphoma, older term) simulate lymphoma clinically and histologically. They can be divided into B-cell predominant (typical cutaneous lymphoid hyperplasia (CLH), angiolymphoid hyperplasia, Kimura's disease, and Castleman's disease) and T-cell predominant (T-cell CLH, lymphomatoid contact dermatitis, and lymphomatoid drug eruption). Both types may represent exaggerated reactions to diverse external antigens (insect bite, tattoo, zoster, trauma, among others). A composite assessment of clinical presentation and behavior, routine histology, immunophenotyping, and molecular studies is essential for the diagnosis of benign cutaneous lymphoid infiltrates. Treatment includes antibiotics, intralesional and systemic corticosteroids, excision, radiotherapy, and immunosuppressants. Treatment depends on the assessment and biologic behavior, which is usually benign. Molecular biologic analysis has shown that a significant proportion of cases harbor occult B- or T-cell clones (clonal CLH). Progression to overt cutaneous lymphoma has been observed in a minority of cases. Patients with clonal populations of B or T cells and persistent lesions should be closely observed for emergence of a lymphoma.