Search PubMed⌕ Search

Biomedical subjects

M Raffeld

Publications and source records attributed to M Raffeld.

At least 109 records · Page 6Linked to original sources
PubMed1994

S-100-positive T-cell lymphoproliferative disorder. A case report and review of the literature.

The authors describe a patient with a S-100-positive T-cell lymphoproliferative disorder, characterized by clinically aggressive behavior, with leukemic dissemination and death within 1 year of the onset of symptoms. The neoplastic cells had abundant amphophilic cytoplasm, suggestive of plasmacytoid differentiation, but demonstrated a mature T-cell immunophenotype characteristic of the suppressor-cytotoxic subset. In addition, the cells expressed the S-100 protein within the cytoplasm. Genotypic studies were performed by Southern blot analysis, which demonstrated beta-chain T-cell receptor gene rearrangement, further confirming the T-cell nature of this disorder. This case had features very similar to those of the seven cases previously reported. It has been proposed that the S-100-positive T-cell lymphoproliferative disorder is a distinctive clinicopathologic entity.

Adult↗
PubMed1994

The interrelationship between Hodgkin's disease and non-Hodgkin's lymphomas.

BACKGROUND: While Hodgkin's disease (HD) and the non-Hodgkin's lymphomas (NHLs) have long been regarded as distinct disease entities, recent observations suggest a closer association. The analysis of cases in which both diseases are present in the same anatomic site (composite lymphomas), or in separate sites (simultaneous or sequential HD and NHL), indicates that this phenomenon occurs more frequently than would be expected by chance alone. DESIGN: We reviewed our experience with composite, simultaneous, and sequential cases of HD and NHL, including both nodular lymphocyte-predominant HD (NLPHD) and the other (so-called 'usual') subtypes of HD. Cases analyzed included 43 cases of NLPHD and large-cell lymphoma (LCL); 14 cases of NHL following HD; 12 cases of composite lymphoma; 2 cases of simultaneous HD and NHL involving different sites; 8 cases of chronic lymphocytic leukemia (CLL) with Reed-Sternberg (RS) cells; and 22 cases of HD following NHL. Immunophenotypic analysis of both components (HD & NHL) was performed when possible. In addition, in situ hybridization for Epstein-Barr virus (EBV) EBER1 mRNA was performed in 35 cases of usual HD associated with NHL. RESULTS: The most common form of composite lymphoma was coexistent NLPHD with LCL of B-cell immunophenotype. With the abnormal cells of NLPHD also being of B-cell lineage, this finding suggests the existence of a clonal relationship between the two components. The association of nodular sclerosis or mixed cellularity HD and NHL was less common but still significant. The vast majority of the NHL associated with HD were of B-cell origin, most commonly follicular lymphomas. EBV was identified more frequently in the NHL of composite NHL + HD (4/12 cases; 33%) than the other patient groups studied (2/23; 9%). Moreover, in 4/5 composite lymphomas both the HD and NHL component were EBV-positive, suggesting an origin from a common EBV-infected progenitor cell. CONCLUSION: These findings suggest that, at least in some cases, HD may be clonally related to an underlying B-cell malignancy, and that the Reed-Sternberg cell may be an altered B lymphocyte. A process that may have a different pathogenesis is the late occurrence of aggressive, usually EBV-negative (12/14 cases), B-cell NHL in patients successfully treated for HD. Such tumors may be related to an underlying and persistent immunodeficiency in these patients, and may be of similar pathogenesis to the Burkitt-like lymphomas associated with HIV-infection.

Diagnosis, Differential↗
PubMed1994

Epstein-Barr virus is infrequently identified in non-Hodgkin's lymphomas associated with Hodgkin's disease.

Epstein-Barr virus (EBV) was identified in a subset of cases of Hodgkin's disease (HD) and in some non-Hodgkin's lymphomas (NHLs), particularly those associated with immunodeficiency. Because patients with HD have associated immune system defects, we hypothesized that EBV might be involved in NHLs associated with HD. Using fixed paraffin sections and in situ hybridization for EBV EBER1 RNA, we studied 12 cases of composite NHL + HD, two patients with NHL who simultaneously also had HD involving a different site (simultaneous HD and NHL), 14 NHLs arising in patients who previously had HD, and seven NHLs from patients who subsequently developed HD. Epstein-Barr virus was identified most frequently in composite NHL + HD. Five (42%) cases of composite NHL + HD contained EBV in Reed-Sternberg and Hodgkin cells, four of which also had EBV-positive NHLs, diffuse mixed or large-cell type, with 10 to more than 50 EBV-positive cells per x400 microscopic field. These results suggest that in this subset of four cases, both the NHL and HD components may have arisen from the same EBV-infected progenitor cell. We did not find EBV in two cases of simultaneous NHL and HD or in seven NHLs preceding development of HD. We identified EBV in only two of 14 NHLs following HD, one small noncleaved cell lymphoma and one plasmacytoma, both containing more than 50 EBV-positive cells per x400 microscopic field. These results suggest that EBV plays a minimal role in NHLs associated with HD, with the exception of composite NHL + HD. Hodgkin's disease-associated immune defects may be involved in the pathogenesis of a subset of NHLs following HD, but the exact pathogenesis of most NHLs associated with HD remains uncertain. Parallels with the high-grade Burkitt-like lymphomas associated with human immunodeficiency virus infection are noted.

Adult↗
PubMed1994

Block of AIDS-Kaposi's sarcoma (KS) cell growth, angiogenesis, and lesion formation in nude mice by antisense oligonucleotide targeting basic fibroblast growth factor. A novel strategy for the therapy of KS.

Kaposi's sarcoma (KS) is the most frequent tumor of HIV-1-infected individuals (AIDS-KS). Typical features of KS are proliferating spindle-shaped cells, considered to be the tumor cells of KS, and endothelial cells forming blood vessels. Basic fibroblast growth factor (bFGF), a potent angiogenic factor, is highly expressed by KS spindle cells in vivo and after injection in nude mice it induces vascular lesions closely resembling early KS in humans. Similar lesions are induced by inoculating nude mice with cultured spindle cells from AIDS-KS lesions (AIDS-KS cells) which produce and release bFGF. Here we show that phosphorothioate antisense (AS) oligonucleotides directed against bFGF mRNA (ASbFGF) inhibit both the growth of AIDS-KS cells derived from different patients and the angiogenic activity associated with these cells, including the induction of KS-like lesions in nude mice. These effects are due to the block of the production of bFGF which is required by AIDS-KS cells to enter the cell cycle and which, after release, mediates angiogenesis. The effects of ASbFGF are specific, dose dependent, achieved at low (0.1-1 microM), nontoxic, oligomer concentrations, and are reversed by the addition of bFGF to the cells, suggesting that ASbFGF oligomers are promising drug candidates for KS therapy.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Diffuse small noncleaved-cell, non-Burkitt's lymphoma in adults: a high-grade lymphoma responsive to ProMACE-based combination chemotherapy.

PURPOSE: To review the efficacy of cyclophosphamide, doxorubicin, etoposide, methotrexate with leucovorin, and prednisone (ProMACE)-based combination chemotherapy programs in the treatment of patients with diffuse small noncleaved-cell non-Burkitt's lymphoma. PATIENTS AND METHODS: Thirty-three patients with diffuse small noncleaved-cell non-Burkitt's lymphoma were accrued: eight with localized disease were treated with modified ProMACE-mechlorethamine, vincristine, procarbazine, and prednisone (MOPP) plus involved-field radiation therapy, and 25 with advanced-stage disease were treated with ProMACE/MOPP flexitherapy (n = 8), ProMACE-MOPP (n = 9), or ProMACE-cytarabine, bleomycin, vincristine, and methotrexate with leucovorin (CytaBOM) (n = 8). The median follow-up duration is 10 years. RESULTS: All eight patients with localized disease achieved a complete response, none have relapsed, and one died of intercurrent illness. Among patients with advanced-stage disease, five of eight (63%) flexitherapy-treated patients, six of nine (67%) ProMACE-MOPP-treated patients, and eight of eight (100%) ProMACE-CytaBOM-treated patients achieved a complete response. If the two ProMACE-MOPP-based groups are considered together, disease-free and overall survival rates at 15 years are projected at 61% and 35%, respectively. In contrast, only one patient has relapsed from a ProMACE-CytaBOM-induced complete remission, and overall survival of ProMACE-CytaBOM-treated patients (88%) is significantly higher than that for flexitherapy and ProMACE-MOPP (P2 = .04). CONCLUSION: Adult patients with diffuse small non-cleaved-cell non-Burkitt's lymphoma may be effectively treated with regimens that are effective in other aggressive lymphomas (eg, diffuse large-cell lymphoma).

Adult↗
PubMed1994

Immunodeficiency-associated malignant lymphoma. Three cases showing genotypic evidence of both T- and B-cell lineages.

Dual rearrangement of both immunoglobulin and T-cell receptor (TCR) genes has been described in up to 30% of precursor lymphoid neoplasms, but this phenomenon occurs rarely in lymphomas with a mature phenotype. We describe three cases of immunodeficiency-associated lymphomas, two in patients with acquired immunodeficiency syndrome (AIDS) and one in a patient with a renal transplant, in which both immunoglobulin and TCR gene rearrangements were identified. Two cases exhibited clonal JH, clonal JK, and clonal TCR beta gene rearrangements; the other case had clonal JK and TCR beta gene rearrangements with deletion of JH. Two of these bigenotypic lesions exhibited a B-cell phenotype, and the other exhibited evidence of both a B- and T-cell phenotype, containing cytoplasmic CD3 as well as monoclonal kappa light chain. In addition, two of the cases exhibited the presence of clonal Epstein-Barr viral DNA. These observations suggest that lymphomas arising in immunodeficiency states may be more prone to disordered differentiation than those arising in an intact immune system.

Adult↗
PubMed1994

An investigation of the viral pathogenesis of Kikuchi-Fujimoto disease. Lack of evidence for Epstein-Barr virus or human herpesvirus type 6 as the causative agents.

Histiocytic necrotizing lymphadenitis of Kikuchi and Fujimoto is a well-defined clinicopathologic entity of unknown cause. Both the Epstein-Barr virus (EBV) and human herpesvirus type 6 (HHV-6) have been suggested as potential etiologic agents. Twenty cases of Kikuchi-Fujimoto disease were studied for the presence of EBV DNA and HHV-6 DNA by the polymerase chain reaction (PCR), and in situ hybridization in the case of EBV. Cellular DNA from sections of formalin-fixed, paraffin-embedded lymph node tissue was amplified using the PCR technique and oligonucleotide primers to the EBV BamH1 W, lymphocyte-determined membrane antigen, or the EBNA-1 region. These studies were performed in three separate laboratories. In addition, 12 cases were examined by in situ hybridization, eight of which had shown at least one positive PCR signal for EBV. The presence of HHV-6 was assessed by PCR using primers to part of the pZVH14 sequence. Biopsy specimens from eight patients (40%) showed a strong positive signal for EBV in at least one laboratory, while an additional three specimens (15%) showed a weaker positive signal. Five cases studied showed rare positive cells by in situ hybridization, and one case had scattered positive cells. All samples lacked HHV-6 genomic templates. These findings indicate that HHV-6 does not play a role in the pathogenesis of Kikuchi-Fujimoto disease and do not implicate EBV as a causal agent for Kikuchi-Fujimoto disease, since EBV was detected in only a fraction of cases with a low number of positive cells detected by in situ hybridization. Further, some discrepancies were identified in the positive results for EBV in samples studied by multiple laboratories. These results indicate that inconsistent results by PCR may occur with very low levels of viral genomes and that different laboratories perform DNA amplification at different efficiencies. Alternatively, laboratory contamination may give rise to false-positive results. Therefore, a positive result for EBV should be interpreted with caution and should be confirmed by repeated study (PCR) or by independent methodology (in situ hybridization).

Adolescent↗
PubMed1993

p53 mutation is associated with progression in follicular lymphomas.

The majority of low-grade follicular lymphomas will eventually transform to an aggressive intermediate, or high-grade lymphoma. The molecular mechanisms responsible for this transformation have not been determined. We studied serial biopsies from 34 patients with follicular lymphomas that underwent histologic transformation, for abnormalities of the p53 tumor suppressor gene by a combination of immunohistochemistry, single strand conformation polymorphism analysis (SSCP), and sequencing. We found overexpression of p53 in 10 of the 34 transformed aggressive lymphomas, 9 of which contained mutations identified by SSCP analysis and subsequent sequencing. Matched pretransformation low-grade follicular lymphoma biopsies were available for 7 of the 10 cases. None of six studied by immunohistochemistry showed overexpression of p53 and only 1 of 4 studied by SSCP/sequencing showed the presence of mutation in the pretransformation biopsy. Interestingly, an eighth p53 positive transformed lymphoma recurred with a clonally related, p53 negative low-grade lymphoma 5 years after the patient had achieved a complete remission. Immunohistochemistry also showed that several pretransformation biopsies from p53 positive transformed cases showed rare p53 positive cells and in one case we could document an increase in their number over time. Twenty-five additional low-grade follicular lymphoma biopsies were also examined. Three patients had lymphomas positive for p53 mutation. One of the three subsequently transformed within a year of the biopsy studied; the second patient had an earlier (unavailable) biopsy at a different site that showed transformed histology. The third patient was treated with ProMACE-MOPP combination chemotherapy and attained a complete remission. We conclude that (1) mutations of p53 are associated with histologic transformation in approximately 25% to 30% of follicular lymphomas and (2) p53 positive cells can be detected before histologic transformation, but do not comprise a significant percentage of the neoplastic cell population (identifiable by SSCP) until late in the disease, just before or after histologic progression. Finally, the data also suggest that p53 positive low-grade lymphomas are at risk for progression and that in this subset, aggressive therapy may be warranted.

Base Sequence↗
PubMed1993

Molecular analysis of the BCL-3 locus at chromosome 17q22 in B-cell neoplasms.

To better understand the role of the BCL-3 locus at chromosome 17q22 in the pathogenesis and progression of leukemias and lymphomas, we examined its genomic configuration in 264 B-cell malignancies and its expression in a smaller subset. Cases studied included 39 chronic lymphocytic leukemias, 58 low-grade follicular lymphomas, 20 mantle cell lymphomas, 30 small noncleaved cell lymphomas, 25 acute lymphoblastic leukemias, 10 acquired immunodeficiency syndrome--related non-Hodgkin's lymphomas, and 44 diffuse mixed- or diffuse large-cell lymphomas. In addition, 38 aggressive lymphomas (transformed follicular lymphomas) derived from previously indolent follicular lymphomas were examined. Southern blot analysis showed BCL-3 locus rearrangement in 4 cases (1.5%), ie, in 3 transformed follicular lymphomas and in 1 indolent follicular lymphoma. All 4 also had BCL-2 rearrangements consistent with their follicular center cell origin. None of the BCL-3 rearranged cases showed MYC gene rearrangement, as reported for the original leukemia that led to the discovery of BCL-3. Pretransformation specimens of all three transformed follicular lymphomas showed the presence of the BCL-3 alteration before histologic progression. In 1 case, serial pretransformation biopsies showed that the BCL-3 rearrangement was acquired during the indolent follicular phase of the patient's disease. Thirty lymphomas, including 2 of the 4 with BCL-3 rearrangement, were also examined for BCL-3 message. All 30, including the 2 with BCL-3 rearrangements, expressed the normal 1.7-kb BCL-3 transcript, at approximately equivalent levels. The data indicate that, although BCL-3 locus alterations are found in only a small fraction of B-cell lymphoid malignancies, they occur primarily in a subset of follicular center cell lymphomas. Interestingly, these alterations appear to be acquired during the indolent (follicular) phase of the disease and they are maintained when histologic transformation takes place. The data also suggest that BCL-3 locus alterations do not result in gross changes of BCL-3 gene expression and do not necessarily involve the MYC gene. Although the preferential involvement of BCL-3 alterations in a small subset of follicular lymphomas that transform suggests a possible link between these abnormalities and progression, further studies are needed to ensure that these alterations are biologically relevant and not simply a manifestation of genomic instability.

B-Cell Lymphoma 3 Protein↗
PubMed1993

B-cell lymphoma after angioimmunoblastic lymphadenopathy: a case with oligoclonal gene rearrangements associated with Epstein-Barr virus.

We describe a patient with angioimmunoblastic lymphadenopathy with dysproteinemia (AILD), who subsequently developed large-cell immunoblastic lymphoma of B-cell immunophenotype. At the time of the initial diagnosis, histologic examination of an inguinal lymph node showed typical features of AILD, and there was no evidence of a monoclonal B-cell population by immunohistochemical analysis. In situ hybridization and Southern blot analysis for Epstein-Barr virus (EBV) were negative. At autopsy 2 years later, the patient had widespread lymph node and organ involvement by large-cell immunoblastic lymphoma of B-cell immunophenotype. Southern blot analysis performed on DNA extracted from lymph nodes, liver, and spleen showed two patterns of Ig heavy chain and kappa light chain gene rearrangements. The T-cell receptor beta chain gene was in the germline configuration. Analysis with an EBV terminal repeat region probe showed two clonal populations that paralleled the Ig gene rearrangement studies. Double-labeling immunohistochemistry and in situ hybridization confirmed the presence of EBV within the neoplastic B cells. The data support the hypothesis that EBV was not etiologically related to AILD in this case, and that EBV proliferation may occur after the onset of the disease. Further, the data suggest that some B-cell lymphomas that arise in the setting of AILD resemble EBV-associated B-cell lymphomas that arise in other immunodeficiency states.

Blotting, Southern↗
PubMed1993

bcl-2 expression in Hodgkin's disease. Correlation with the t(14;18) translocation and Epstein-Barr virus.

In a prior study from our laboratory using the polymerase chain reaction (PCR) technique, the t(14;18)(q32;q21) translocation was detected in low copy number in 32% of Hodgkin's disease cases. The cell of origin of the t(14;18), however, was not determined. To further investigate the role of bcl-2 in Hodgkin's disease and the possibility that the translocation resides in Reed-Sternberg and Hodgkin's (RS-H) cells, we analyzed selected cases of Hodgkin's disease immunohistologically using a monoclonal antibody reactive with bcl-2. Because Epstein-Barr virus (EBV) has been reported to upregulate bcl-2 expression, we also used an in situ method for detecting EBV in these tissues. Thirteen cases of Hodgkin's disease were studied, including seven cases with the t(14;18) translocation and six cases without it, as determined by PCR in a prior study. bcl-2 protein was detected immunohistologically in the RS-H cells in eight cases: three with the t(14;18) translocation and five in which the translocation was not detected. EBV RNA was detected in the RS-H cells of four patients, including two in which the RS-H cells also were bcl-2 positive. The presence of bcl-2 staining of the RS-H cells in this series of cases did not correlate with clinical features, histologic subtype, the presence of the t(14;18) translocation, or EBV-positivity. The lack of consistent bcl-2 protein expression in RS-H cells, including EBV-positive RS-H cells, may suggest that the t(14;18) translocation does not reside in RS-H cells in at least a subset of cases of Hodgkin's disease. If this is true, the t(14;18) translocation may not play an important role in the pathogenesis of Hodgkin's disease.

Adolescent↗
PubMed1993

Follicular center cell lymphoma with the t(14;18) translocation in which the rearranged BCL-2 gene is silent.

Using reverse transcription and the polymerase chain reaction (RT-PCR), we determined the level of expression of BCL-2/IgH in 18 follicular center cell lymphomas containing a t(14;18) translocation involving the major breakpoint region and five non-neoplastic lymph nodes. BCL-2/IgH transcripts were demonstrated in 16 follicular center cell lymphoma cases (five high, 11 low) and were not present in any of the five non-neoplastic lymph nodes. In the two follicular lymphoma cases in which BCL-2/IgH transcripts could not be detected by RT-PCR, PCR amplification of genomic DNA indicated this was not due to primer selection. In addition, non-expression was confirmed at the protein level by immunoperoxidase studies. We therefore conclude that these represent true negative cases. This is the first time primary follicular lymphoma cases have been quantitatively studied at the RNA level for expression of BCL-2. We conclude that RT-PCR is a sensitive method for determining levels of expression of this oncogene and may be useful in studying the involvement of BCL-2 in follicular lymphoma.

Adult↗
PubMed1993

Low-grade B-cell lymphoma of mucosa-associated lymphoid tissue arising in the kidney.

We describe a malignant lymphoma arising in the kidney that exhibited clinical and histologic features of low-grade B-cell lymphoma of mucosa-associated lymphoid tissue (MALT). Clinically, the neoplasm involved the kidney and one perirenal lymph node (stage IIE) and did not recur or disseminate following nephrectomy, lymphadenectomy, and local radiation therapy. Histologically, the neoplasm recapitulated the features of low-grade B-cell lymphomas of MALT at other sites. The neoplastic cells resembled centrocyte-like cells, some of which formed lymphoepithelial lesions with renal tubules, and reactive lymphoid follicles were scattered within the neoplasm. The neoplastic cells expressed monotypic cytoplasmic Ig kappa. Low-grade B-cell MALT lymphomas arising in the kidney are rare. Their occurrence further demonstrates the diversity of anatomical sites that may be involved by MALT lymphomas. In addition, this neoplasm also had histologic and cytologic features resembling those of monocytoid B-cell lymphoma, supporting the hypothesis that low-grade B-cell lymphomas of MALT and monocytoid B-cell lymphomas are closely related and may be two morphological manifestations of the same neoplasm.

Aged↗
PubMed1993

Clustered mutations in the second exon of the MYC gene in sporadic Burkitt's lymphoma.

The primary tumors from 15 untreated patients with Burkitt's lymphoma were analysed for abnormalities in the coding region of the MYC gene by single stranded conformational polymorphism (SSCP) analysis followed by DNA sequencing. Fourteen of the 15 tumors had one or more clonal mutations. Forty one mutations were found in the second exon; only one occurred in the third exon. Seven tumors had mutations that clustered in a region spanning amino acids 38-63. Four of these possessed mutations that altered prolines at positions 57 (3), 60 (1), and 63 (1). Seven tumors were mutated in the central portions of the second exon. These occurred at position 95 (2), position 115 (2), position 137 (1), and position 138 (3). Analysis of the published sequences from five lymphoma cell lines and one primary tumor showed a similar clustering of mutations, with all six having mutations in codons between positions 38-63. The regions where mutations occurred have been associated with a variety of properties, including transcriptional activation and cellular transformation. The number and location of mutations showed no correlation with either chromosome 8 or chromosome 14 breakpoints or with the Epstein-Barr virus positivity of the tumors. This unexpected, frequent occurrence of clustered mutations in the second exon of the MYC gene suggests a role for the mutated MYC proteins in the pathogenesis of Burkitt's lymphoma, possibly through altered interactions of this domain with other cellular factors.

Amino Acid Sequence↗
PubMed1992

Helper virus induced T cell lymphoma in nonhuman primates after retroviral mediated gene transfer.

Moloney Murine Leukemia Virus (MoMuLV) causes T cell neoplasms in rodents but is not known to be a pathogen in primates. The core protein and enzyme genes of the MoMuLV genome together with an amphotropic envelope gene are utilized to engineer the cell lines that generate retroviral vectors for use in current human gene therapy applications. We developed a producer clone that generates a very high concentration of retroviral vector particles to optimize conditions for gene insertion into pluripotent hematopoietic stem cells. This producer cell line also generates a much lower concentration of replication-competent virus that arose through recombination. Stem cells from rhesus monkeys were purified by immunoselection with an anti-CD34 antibody, incubated in vitro for 80-86 h in the presence of retroviral vector particles with accompanying replication-competent virus and used to reconstitute recipients whose bone marrow had been ablated by total body irradiation. The retroviral vector genome was detected in circulating cells of five of eight transplant recipients of CD34+ cells and in the circulating cells of two recipients of infected, unfractionated bone marrow mononuclear cells. Three recipients of CD34+ cells had a productive infection with replication-competent virus. Six or seven mo after transplantation, each of these animals developed a rapidly progressive T cell neoplasm involving the thymus, lymph nodes, liver, spleen, and bone marrow. Lymphoma cells contained 10-50 copies of the replication-competent virus, but lacked the retroviral vector genome. We conclude that replication-competent viruses arising from producer cells making retroviral vectors can be pathogenic in primates, which underscores the importance of carefully screening retroviral producer clones used in human trials to exclude contamination with replication-competent virus.

Animals↗
PubMed1992

An overview of the classification of non-Hodgkin's lymphomas: an integration of morphological and phenotypical concepts.

An analysis of trends in the incidence of non-Hodgkin's lymphoma requires an understanding of individual disease entities within this broad group. The non-Hodgkin's lymphomas represent a diverse group of malignancies that have in common an origin from lymphoid cells. Nevertheless, these disorders are heterogeneous in their clinical behavior, morphological appearance, cellular origin, etiology, and pathogenesis. A modern classification of non-Hodgkin's lymphomas must include an integration of morphological, immunophenotypical, and molecular concepts in order to delineate individual diseases within this broad group. Existing classification schemes such as the working formulation, while they may be useful in providing a guide to clinical management, cannot provide this information in the absence of other data. This point is most readily made with the low-grade B-cell lymphomas which include follicular lymphomas, mantle cell lymphomas, small lymphocytic lymphomas, immunosecretory disorders, and lymphomas of mucosa-associated lymphoid tissues. Each of these malignancies has a distinct phenotype and genotype, and indubitably each has a different etiology. The postthymic T-cell tumors are equally diverse. Analysis of epidemiological data from cancer registries must include a recognition that our ability to recognize individual diseases from historical data is limited. Studies of trends in the non-Hodgkin's lymphomas should attempt to delineate biological markers that may be of relevance to pathogenesis in both historical and prospectively accrued cases.

Humans↗