In aggregate, these results strongly suggest that inappropriate expression of ALK is not involved in the pathogenesis of these CD30+ lymphoproliferative disorders, and that lymph node-based CD30+ large cell lymphoma is a disease that is biologically distinct from skin-based CD30+ lymphoproliferative disorders and Hodgkin's disease.
The aggregate results of these studies indicate that the t(2;5) translocation or other somatic mutations resulting in inappropriate expression of ALK are involved rarely if at all in the pathogenesis of Hodgkin's disease, but may be present in about 10% of cases of lymphomatoid papulosis and 20% of cases of CD30+ primary cutaneous large cell lymphoma.
This translocation creates a novel fusion protein, NPM-ALK, which has transforming properties in vitro and can cause large-cell lymphoma in vivo when transfected into murine bone marrow.
To evaluate this entity in a pediatric population, 36 cases of childhood large cell lymphoma were evaluated for abnormalities of the anaplastic lymphoma kinase (ALK) gene that has been associated with ALCL morphology and immunophenotype.