Both lymphomas and lymphoid leukemias are included in this classification because both solid and circulating phases are present in many lymphoid neoplasms and distinction between them is artificial.For example, B-cell chronic lymphocytic leukemia (CLL) and B-cell small lymphocytic lymphoma are simply different manifestations of the same neoplasm, as are lymphoblastic lymphomas and acute lymphocytic leukemias.Of patients with aggressive NHL, more than 50% can be cured.The vast majority of relapses occur in the first 2 years after therapy.In 1982, results of a consensus study were published as the Working Formulation. The Working Formulation combined results from six major classification systems into one classification.This allowed comparison of studies from different institutions and countries.The Rappaport classification, which also follows, is no longer in common use.As the understanding of NHL has improved and as the histopathologic diagnosis of NHL has become more sophisticated with the use of immunologic and genetic techniques, a number of new pathologic entities have been described. In addition, the understanding and treatment of many of the previously described pathologic subtypes have changed.
Follicular lymphoma and primary follicular lymphoma of the duodenum are particularly indolent variants that rarely progress and rarely require therapy.[20,21] A so-called pediatric-type nodal follicular lymphoma has indolent behavior and rarely recurs; adult patients with this histologic variant are characterized by a lack of rearrangement in conjunction with a Ki-67 proliferation index greater than 30% and a localized stage I presentation. Patients with indolent lymphoma may experience a relapse with a more aggressive histology.
Within the B-cell and T-cell categories, two subdivisions are recognized: precursor neoplasms, which correspond to the earliest stages of differentiation, and more mature differentiated neoplasms.[9,10] Follicular lymphoma comprises 20% of all NHL and as many as 70% of the indolent lymphomas reported in American and European clinical trials.[1-3] Most patients with follicular lymphoma are age 50 years and older and present with widespread disease at diagnosis.