The immunocytochemical detection of NPM-ALK (and proteins encoded by other ALK fusion genes) has allowed the definition of a tumor entity, "ALK-positive lymphoma" (which shows only partial overlap with pathologists' diagnosis of ALCL), to be defined and is invaluable in distinguishing this disease from ALK-negative large cell lymphomas.     ///    "Biochemical studies suggest an anti-apoptotic function of NPM-ALK, and this may contribute to oncogenesis. "