Theresa Marafioti

Origin of Nodular Lymphocyte-Predominant Hodgkin's Disease from a Clonal Expansion of Highly Mutated Germinal-Center B Cells

BACKGROUND The atypical cells of nodular lymphocyte-predominant Hodgkins disease, designated lymphocytic and histiocytic (L&H) cells, have a B-cell phenotype. To clarify the clonality of these cells, we studied rearranged immunoglobulin genes for the variable region of the heavy chain (V[H] genes) in individual L&H cells from 11 patients with nodular lymphocyte-predominant Hodgkins disease. We also studied the expression of immunoglobulin light chains by those cells in six of the same patients. METHODS Single CD20+ L&H cells were isolated from frozen sections by a technique of micromanipulation. The rearranged V(H) genes of these cells were amplified by the polymerase chain reaction (PCR), sequenced, and compared with germ-line V(H) genes. Immunoglobulin light-chain messenger RNA (mRNA) was detected by in situ hybridization. RESULTS Of 615 L&H cells isolated from all the frozen sections, 160 yielded PCR products. In each of the 11 patients, the L&H cells that could be evaluated had identically rearranged V(H) genes, whether they were isolated from the same nodule, different nodules, or different blocks of tissue. All the V(H) sequences derived from the L&H cells were highly mutated (7.5 to 27.2 percent). In two cases the coding capacity of the V(H) genes was completely or partially disrupted by mutations. Intraclonal diversity was found in six cases, and monotypic immunoglobulin light-chain mRNA was found in six. CONCLUSIONS The L&H cells of nodular lymphocyte-predominant Hodgkins disease represent a monoclonal expansion of B cells. The high load of V(H) gene mutations and signs of intraclonal diversity suggest a relation between L&H cells and germinal-center B cells at the centroblastic stage of differentiation.

Classical Hodgkin's Disease and Follicular Lymphoma Originating From the Same Germinal Center B Cell

PURPOSE Classical Hodgkins disease and non-Hodgkins B-cell lymphoma occasionally occur in the same patient. To clarify whether these different diseases share a common precursor cell, we analyzed the immunoglobulin rearrangements in tumor cells of the classical Hodgkins disease and the follicular lymphoma that developed in the same patient 2 years apart. PATIENTS AND METHODS Polymerase chain reaction (PCR) for the detection of rearranged immunoglobulin genes was carried out on single Reed-Sternberg cells and on whole tissue DNA extracted from the follicular lymphoma. PCR products were sequenced and compared with each other and with germ line immunoglobulin variable segments. Immunoglobulin heavy- and light-chain transcripts were analyzed by radioactive in-situ hybridization. RESULTS The same monoclonal immunoglobulin gene rearrangement was found in both neoplasms. The variable region of the immunoglobulin heavy-chain genes of the Reed-Sternberg and of the follicular lymphoma cells were differently mutated, but six somatic mutations were shared by both lymphoma cells. Although the coding capacity of the immunoglobulin genes was preserved in both neoplastic cell populations, immunoglobulin heavy- (mu) and light- (kappa) chain expression was restricted to the follicular lymphoma cells, except for small amounts of kappa light-chain mRNA in some Reed-Sternberg cells. CONCLUSIONS The neoplastic cells of the Hodgkins disease and the follicular lymphoma that occurred in this patient derived from a common precursor B cell. Its differentiation stage could be identified as that of a germinal center B cell. Thus, transforming events can be more important than the cell of origin in determining a disease entity.

Clonality of Reed-Sternberg cells in Hodgkin's disease.

To the Editor: In 1995 we reported in the Journal the results of a molecular analysis of single Reed–Sternberg cells in biopsy specimens from patients with Hodgkins disease.1 Amplified immunoglobu...