Conventional methods of non-Hodgkin's lymphoma (NHL) diagnosis and classifi
cation are based principally on morphology and immunophenotype and have sig
nificant shortcomings in the diagnosis of large-cell lymphoma. Rather than
being discriminatory, morphological and immunophenotypic parameters have re
vealed a significant heterogeneity in the large-cell lymphomas and for the
most part have failed to detect distinct clinically and biologically meanin
gful subsets. More specific pathogenic molecular markers are clearly needed
to define further and to separate specific clinicopathological entities wi
thin large-cell lymphoma for targeted therapy. As detailed in this review,
the discovery of anaplastic lymphoma kinase (ALK) has permitted the definit
ion of a distinct molecular genetic subtype of NHL within the clinically an
d pathologically heterogeneous group of CD30(+) lymphomas.