Cutaneous Ki-1 lymphoma: pathology, immunology and clinical characteristics

This paper describes a newly recognized clinicopathologic syndrome of regressing cutaneous nodules, peripheral lymphadenopathy and fever occurring mainly in children and adolescents. Skin lesions show pseudoepitheliomatous hyperplasia, absence of epidermotropism and pleomorphic large lymphoma cells infiltrating the dermis and subcutaneous fat. Lymph nodes have a distinctive appearance with lymphoma cells in sinuses and paracortex. Despite their usual histiocyte-like appearance, the lymphoma cells in most cases have an aberrant T-cell phenotype, expressing several activation antigens including Hodgkin's disease associated antigen Ki-1 (CD30). Clonal rearrangements of the beta chain genes for the T-cell antigen receptor (TCR) were found and revealed a T-cell origin in one case lacking T-cell surface antigens. Identical rearrangements of the TCR genes indicated a monoclonal origin for separate lesions on the arm and leg of another patient. Treatment results in the first group of patients indicate that radiation treatment of an affected area is associated with frequent relapse at other sites, but multiagent chemotherapy (COMP or D-COMP) produces durable remissions in nearly all patients. Bone marrow transplantation was effective salvage therapy for treatment failures. Further studies are underway to investigate the mechanism(s) of tumor regression, the epidemiology, and etiology of Ki-1+ lymphomas which appear to be relatively more frequent in Oriental and Black patients, and in which the first lesion may resemble an insect bite.