A study of lymphoma of large granular lymphocytes with modern modalities: report of two cases and review of the literature

A survival study and prognostic factors analysis on acute promyelocytic leukemia at a single center

This study was aimed to investigate the factors influencing long-term survival on patients with acute promyelocytic leukemia. Here, we present a single center retrospective study with long-term follow-up to explore the prognostic factors and a rationale of the using of ATRA, chemotherapy and As(2)O(3) in the treatment of newly diagnosed APL patients. In total, 222 patients, 184 achieved complete remission (CR) with the CR rate of 82.88% and 22 patients died during early induction therapy with the early-death-rate of 10%. Total 171 newly diagnosed APL patients entering CR were retrospectively analyzed from November 1989 to December 2004,with a median follow-up of 36 months (6-185 months). Univariate and multivariate analysis of eight factors potentially influencing survival and prognosis were carried out with Log-Rank and Cox regression method, including sex, age, initial WBC count, the level of lactic dehydrogenase (LDH), first induction regimen, days from induction therapy to CR, post-remission therapy and the status of PML-RAR alpha fusion gene by reverse transcription-polymerase chain reaction (RT-PCR). The results showed that the estimated 5-year overall survival (OS) and relapse-free survival (RFS) were 80.9+/-4.0 and 71.0+/-4.0%, respectively. Univariate analyses showed that initial WBC count, first induction regimen, days from induction therapy to CR, post-remission therapy regimen and the status of PML-RAR alpha in remission were important prognostic factors for long-term survival. Multivariate study showed that only post-remission therapy regimen was associated with RFS and OS. It is concluded that the post-remission treatment combining ATRA, As(2)O(3) and chemotherapy would significantly improve the long-term survival of APL patients achieving CR(1).

Aggressive natural killer-cell leukemia revisited: large granular lymphocyte leukemia of cytotoxic NK cells

Aggressive natural killer-cell leukemia (ANKL) is a rare form of large granular lymphocyte leukemia, which is characterized by a systemic proliferation of NK cells. The clinical features of 22 ANKL cases were analyzed. Hepatomegaly (64%), splenomegaly (55%) and lymphadenopathy (41%) were also frequently observed. Leukemic cells were identified as CD1-, CD2+, surface CD3-, CD4-, CD5-, CD7+, CD8+/-, CD10-, CD11b+/-, CD13-, CD16+, CD19-, CD20-, CD25-, CD33(-), CD34-, CD38+, CD56+, CD122+, HLA-DR+ and TCR-. Two of the 16 cases examined for CD57 were positive and three of the seven cases examined for cytoplasmic CD3. Epstein-Barr virus was detected in the tumor cells of 11 of the 13 cases examined. No common cytogenetic abnormalities were identified and 6q anomaly was detected in only one. Three of 13 patients treated with chemotherapy containing anthracycline/anthraquinone attained complete remission, in contrast to none of the eight who were treated with regimens without anthracycline. Although the overall prognosis was poor with a median survival of 58 days, those who attained remission showed better prognosis (P=0.005). These findings suggest that ANKL is an entity of mature cytotoxic NK-cell neoplasms with distinct phenotype and disease presentations. Intensive treatment for ANKL may result in a better prognosis.

Genomic alterations in blastic natural killer/extranodal natural killer-like T cell lymphoma with cutaneous involvement

Natural killer and natural killer-like T cell lymphomas represent a rare type of non-Hodgkin's lymphoma originally described to involve the upper aerodigestive tract. This malignancy has been increasingly observed in other extranodal sites, particularly in the skin. Patients with cutaneous natural killer cell lymphoma generally have a poor prognosis; however, the etiology and the underlying molecular pathogenesis remain unclear. This study aimed to investigate comprehensively genomic changes in blastic natural killer and extranodal natural killer-like T cell lymphoma with cutaneous involvement. Comparative genomic hybridization showed chromosome imbalances in six of eight cases studied (75%). The mean number of chromosome imbalances per sample was 2.18+/-1.63 with similar number of gains (1.18+/-1.17) and losses (1.00+/-1.34). The most frequent DNA copy number changes observed were losses of 9/9p (83%), followed by loss of 13q and gain of 7 (67%). Similar patterns of chromosome imbalances were observed in both blastic natural killer and cutaneous natural killer-like T cell lymphomas. Loss of the RB1 gene at 13q14.2 was detected in one blastic natural killer cell lymphoma with 13q loss using a gene dosage assay, and in one cutaneous natural killer-like T cell lymphoma without 13q loss using fluorescent in situ hybridization. Genomic microarray analysis identified oncogene copy number gains of PAK1 and JUNB in three of four cases studied, and gains of RAF1, CTSB, FGFR1, and BCR in two cases. Real-time polymerase chain reaction detected amplification of CTSB and RAF1 in four of five cases analyzed, JUNB and MYCN in three cases, and REL and YES1 in two cases, respectively. In conjunction with this study, an extensive literature search for the published G-banded karyotypes of four subsets of natural killer cell lymphomas was conducted, which showed a nonrandom pattern of multiple chromosome aberrations. These results reveal consistent genetic alterations in cutaneous natural killer cell lymphomas, and provide a basis for further investigation of molecular pathogenesis in this malignancy.

Cytotoxic/natural killer cell cutaneous lymphomas. Report of EORTC Cutaneous Lymphoma Task Force Workshop

BACKGROUND

Cutaneous lymphomas expressing a cytotoxic or natural killer (NK) cell phenotype represent a group of lymphoproliferative disorders for which there is currently much confusion and little consensus regarding the best nomenclature and classification.

METHODS

This study analyzes 48 cases of primary cutaneous lymphoma expressing cytotoxic proteins and/or the NK cell marker, CD56. These cases were collected for a workshop of the European Organization for Research and Treatment of Cancer Cutaneous Lymphoma Task Force, to better clarify the clinical, morphologic, and phenotypic features of these uncommon tumors.

RESULTS

Several categories with different clinical and pathologic features were delineated: 1) aggressive, CD8+, epidermotropic, cytotoxic T-cell lymphoma; 2) mycosis fungoides, cytotoxic immunophenotype variant; 3) subcutaneous panniculitis-like T-cell lymphoma; 4) NK/T-cell lymphoma, nasal type; 5) CD4+, NK cell lymphoma; 6) blastoid NK cell lymphoma; (7) intravascular NK-like lymphoma; and 8) cytotoxic, peripheral T-cell lymphoma.

CONCLUSIONS

Our data show that primary cutaneous cytotoxic/NK cell lymphomas include distinct groups of diseases, clinically, histologically, and biologically. Because the finding of a cytotoxic phenotype often has prognostic significance, the routine use of cytotoxic markers in the diagnosis and classification of cutaneous lymphomas should be expanded.

Deletion 6q as a recurrent chromosomal aberration in T-cell large granular lymphocyte leukemia

T-cell large granular lymphocyte (T-LGL) leukemia is an uncommon disease, with limited information on karyotypic aberrations. No consistent chromosomal changes have thus far been described. We report two cases of T-LGL leukemia who presented with severe anemia. The LGL were CD3+, CD4-, CD8+, CD56-, and CD161-, with variable expression of CD94, CD158a, and CD158b, and had clonal T-cell receptor gene rearrangement. A deletion of the long arm of chromosome 6 was the sole aberration in both cases. This is the first report of a recurrent chromosomal aberration in T-LGL leukemia.

Acute promyelocytic leukemia with a PLZF-RARalpha fusion protein

In most cases of acute promyelocytic leukemia (APL), a fusion of the promyelocytic leukemia (PML) and the retinoic acid receptor-alpha (RARalpha) genes occurs, resulting in the expression of a PML-RARalpha chimeric protein. In approximately 1% of the cases of APL, variant chromosomal aberrations may be found fusing RARa with other genes. Four variant mutations have been described, and the t(11;17)(q21;q23) translocation generating a promyelocyte leukemia zinc finger (PLZF)-RARalpha fusion gene is the most common. PLZF-RARalpha-positive APL forms a clinically distinct group because unlike PML-RARalpha-positive leukemia, it does not respond to retinoic acid with terminal granulocytic differentiation of the cells, and remissions cannot be achieved with retinoids alone. At the molecular level, this has been explained by the retinoic acid-insensitive binding of corepressor proteins to the PLZF part of the fusion protein, leading to sustained repression of target genes that are important for cellular differentiation. Targeting of the PLZF-RARalpha-bound corepressor complexes using a combination of all-trans retinoic acid (ATRA) and deacetylase inhibitors has shown that the repression of target genes can be relieved, allowing differentiation of the cells. In addition, when a combination of retinoic acid and the hematopoietic growth factor granulocyte colony-stimulating factor (G-CSF) is applied, the cells may be forced to undergo terminal differentiation, both in vitro and in vivo. This suggests that signals from the activated G-CSF receptor may induce the release of corepressor proteins from PLZF. Together, these findings indicate that PLZF-RARalpha-positive leukemia is not completely resistant to differentiation induction if the proper costimuli are given.

Cytogenetic abnormalities in natural killer cell lymphoma/leukaemia--is there a consistent pattern?

The group of putative natural killer cell lymphomas, also known as NK/T cell lymphomas (nasal and nasal-type) has been characterized only in recent years. Whilst a good amount of clinical information has been gathered on this group of uncommon lymphoid neoplasms, there is little information on the cytogenetic or molecular alterations. A review of the literature shows that chromosomal abnormalities are indeed commonly found in these tumours, and aberrations involving chromosome 6q are most frequent. Other non-random abnormalities include +X, i(1q), i(7q), +8, del(13q), del(17p), i(17q), and 11q23 rearrangement. It appears that deletions of the chromosome 6 at around q21-23 region is the commonest recurrent chromosomal abnormality, and fluorescence in situ hybridisation studies have confirmed the occurrence of deletions at 6q22-23 in the CD3- CD56+ tumour cells. Search for the involved genes located in this chromosome region can potentially shed light on the molecular pathogenesis of the natural killer cell neoplasms.

T-cell lymphoma associated with natural killer-like T-cell reaction

We report a case of T-cell lymphoma showing in the peripheral blood (PB) exclusively T-lymphocytes with suppresser T-cell preponderance and a high percentage of natural killer (NK) marker positive cells by flow cytometry. A T-cell receptor (TCR) gene analysis of the PB leukocytes demonstrated rearrangements of TCRalpha, TCRbeta, and TCRgamma genes. Therefore, the phenotype and genotype appeared to be consistent with an NK-like T-cell leukemia/lymphoma. However, when the PB lymphocytes were separated by size, it was found that 80% of NK marker positive cells were in the smaller cell population, while the neoplastic cells were in the large cell gate. A diagnosis of T-cell lymphoma with reactive NK-like T-cells was finally confirmed by demonstrating the presence of both large atypical lymphoid cells and large granular lymphocytes (LGL) on PB smears. Although immunoperoxidase stain of bone marrow and colon showed positive T-cell markers in the tumor cell population, cytoplasmic granules could not be identified in tissue sections and, thus, a distinction between T-cell lymphoma and NK-like T-cell lymphoma could not be made by light microscopy until NK markers were studied. CD57 was demonstrated immunohistochemically in small lymphocytes but not in the large tumor cells in the colon. Electron microscopy, however, demonstrated LGL reaction to the lymphoma cells in the colonic biopsy. NK-like T-cell lymphoma usually carries a poorer prognosis than peripheral T-cell lymphoma, thus the distinction of these neoplasms is important. This study emphasizes that T-cell lymphoma may cause an LGL reaction or proliferation. If the lymphoma cells were of the same size as LGL, flow cytometric studies may have misled the diagnosis to NK-like T-cell-lymphoma.

CD56-positive (nasal-type T/NK cell) lymphoma arising on the skin. Report of two cases and review of the literature

Several authors have reported cases of patients with malignant lymphoma with unique characteristics, designated nasal-type T/NK cell lymphoma, which expresses the natural killer (NK) cell marker and shows frequent extra-nodal involvement and poor prognosis. We report 2 cases of this type of lymphoma which were CD56-positive and showed a histopathologically angiocentric pattern with cutaneous and subcutaneous tumorous lesions. Patient 1 had extensive invasion of skin, underlying skeletal muscle, spleen and bone marrow, and died of sepsis 34 months after onset. Patient 2 had multiple subcutaneous nodules and invasion to mammary gland, lung, lymph node and spleen at the time of her first visit. She died of a rapid invasion of lymphoma cells to the liver 5 months after onset. Both patients showed similar immunophenotypes of tumor cells (CD2+, CD3-, CD4-, CD8-, CD20-, CD56+) and germ line configuration of the heavy chain of immunoglobulin (JH), T-cell receptor C beta-1 subunit DNA and T-cell receptor J gamma subunit DNA. Epstein-Barr virus early regions RNA was demonstrated in the nuclei of tumor cells of both patients with in situ hybridization. The histopathological examination of the skin lesions of both patients revealed the features of angiocentric lymphoma. The detection of CD56 in the tumor cells of cutaneous lymphomas should be routinely performed for the early diagnosis of this type of lymphoma with extremely poor prognosis.

CD56/neural cell adhesion molecule expression in primary extranodal Ki-1/CD30+ lymphoma. Report of a pediatric case with simultaneous cutaneous and bone localizations

We describe the clinicopathologic features of an unusual case of CD30+/CD50+ T-cell lymphoma in a child who presented with simultaneous primary extranodal cutaneous and bone localizations. The expression of CD56 (neural cell adhesion molecule, or NCAM) is rare in non-Hodgkin's lymphomas other than in a group of haematopoietic/lymphoid neoplasms of natural killer and natural killer-like T-cells, which usually involve extranodal sites and often pursue an aggressive clinical behavior. Coexpression of CD30 and CD56 in T-cell lymphomas is exceedingly rare, and its biological significance is unknown. Our patient responded well to an intensive chemotherapy regimen, and she is now in complete remission 4 years after discontinuation of chemotherapy. Expression of NCAM could be regarded as responsible, in part, for the extranodal localization of lymphoma cells; expression of CD56 also might contribute to the definition of a subset of CD30+ lymphomas with distinctive clinicopathologic features.

Primary gastric T-cell lymphoma with and without human T-lymphotropic virus type 1

BACKGROUND

Gastric T-cell lymphomas are rare, and their incidence and viral status have not yet been fully clarified.

METHODS

Sixty-seven cases of surgically resected gastric lymphomas from city hospitals in Tokyo were evaluated. The surface phenotype was determined by immunohistochemistry, gene rearrangement by Southern blot hybridization, association with Epstein-Barr virus (EBV) by EBV-encoded small RNAs in situ hybridization, and the presence of human T-cell lymphotropic virus type 1 (HTLV-1) by serology, Southern blot hybridization, and polymerase chain reaction analysis.

RESULTS

Five of the 67 cases were T-cell lymphoma (7%): 3 cases were HTLV-1 negative (-) and 2 were HTLV-1 positive (+). Systemic eosinophilia was observed in the three HTLV-1(-) gastric lymphomas. Neoplastic cells were morphologically similar in both groups, but a granulomatous reaction with marked eosinophilia was observed only in the two cases of HTLV-1(-) lymphoma. They also had characteristics of natural killer (NK) cell-like T-cell lymphoma, expressing NK markers and TCRgamma gene rearrangement. Positivity with HML-1 (specific for intestinal epithelial T-cells lymphoma was observed in one HTLV-1(+) lymphoma. The EBV gene was detected in only one case of B-cell lymphoma but not in any case of T-cell lymphoma.

CONCLUSIONS

Gastric T-cell lymphoma occurs in 7% of gastric lymphomas in Japan and is comprised of HTLV-1-related lymphomas and lymphomas unrelated to HTLV-1, including NK cell-like lymphomas with eosinophilia.

T-cell lymphoma of CD3+CD4+CD56+granular lymphocytes with hemophagocytic syndrome

A case of T-cell lymphoma of granular lymphocyte (GL) morphology and CD3+CD4+CD56+ phenotype is reported. The lymphoma originated in the subcutaneous tisse of the right thigh and subsequently infiltrated into various organs including the lymph nodes, peripheral blood, bone marrow, skin, lungs, liver, spleen, and peritoneal cavity, and the patient finally developed a hemophagocytic syndrome. The lymphoma cells were positive for CD2, CD3, CD4, and CD56, and negative for CD8, CD16, CD20, and CD57. An identical clonal rearrangement of the T-cell receptor beta chain genes was detected in cells from a lymph node, peripheral blood, and ascites fluid, indicating the monoclonal proliferation of T cells in such organs. This is a T-cell GL lymphoma, expressing the unusual phenotype of CD3+CD4+CD8-CD16-CD56+, which has not been previously reported. The development of hemophagocytic syndrome has also to our knowledge not previously been reported in T-cell GL lymphoma.

Nonnasal Lymphoma Expressing the Natural Killer Cell Marker CD56: A Clinicopathologic Study of 49 Cases of an Uncommon Aggressive Neoplasm

Expression of the natural killer (NK) cell antigen CD56 is uncommon among lymphomas, and those that do are almost exclusively of non–B-cell lineage and show a predilection for the nasal and nasopharyngeal region. This study analyzes 49 cases of nonnasal CD56+ lymphomas, the largest series to date, to characterize the clinicopathologic spectrum of these rare neoplasms. All patients were Chinese. Four categories could be delineated. (1) Nasal-type NK/T cell lymphoma (n = 34) patients were adults 21 to 76 years of age (median, 50 years), including 25 men and 9 women. They presented with extranodal disease, usually in multiple sites. The commonest sites of involvement were skin, upper aerodigestive tract, testis, soft tissue, gastrointestinal tract, and spleen. Only 7 cases (21%) apparently had stage I disease. The neoplastic cells were often pleomorphic, with irregular nuclei and granular chromatin, and angiocentric growth was common. The characteristic immunophenotype was CD2+ CD3/Leu4− CD3ε+ CD56+, and 32 cases (94%) harbored Epstein-Barr virus (EBV). Follow-up information was available in 29 cases: 24 died at a median of 3.5 months; 3 were alive with relapse at 5 months to 2.5 years; and 2 were alive and well at 3 and 5 years, respectively. (2) Aggressive NK cell leukemia/lymphoma (n = 5) patients presented with hepatomegaly and blood/marrow involvement, sometimes accompanied by splenomegaly or lymphadenopathy. The neoplastic cells often had round nuclei and azurophilic granules in the pale cytoplasm. All cases exhibited an immunophenotype of CD2+ CD3/Leu4− CD56+ CD16− CD57− and all were EBV+. All of these patients died within 6 weeks. (3) In blastoid NK cell lymphoma (n = 2), the lymphoma cells resembled those of lymphoblastic or myeloid leukemia. One case studied for CD2 was negative and both cases were EBV−. One patient was alive with disease at 10 months and one was a recent case. (4) Other specific lymphoma types with CD56 expression (n = 8) included one case each of hepatosplenic γδ T-cell lymphoma and S100 protein+ T-cell lymphoproliferative disease and two cases each of T-chronic lymphocytic/prolymphocytic leukemia, lymphoblastic lymphoma, and true histiocytic lymphoma. All of these cases were EBV−. Six patients died at a median of 6.5 months. Nonnasal CD56+ lymphomas are heterogeneous, but all pursue a highly aggressive clinical course. The nasal-type NK/T-cell lymphoma and aggressive NK cell leukemia/lymphoma show distinctive clinicopathologic features and a very strong association with EBV. Blastoid NK cell lymphoma appears to be a different entity and shows no association with EBV.

Pathogenesis and management of acute promyelocytic leukemia

Acute promyelocytic leukemia, formerly a highly lethal disease, was recently shown to be highly responsive to treatment with the natural retinoid, all-trans retinoic acid. This compound induces terminal differentiation of the malignant cells and produces complete remission in most patients with this disease. The clinical response is due in part to the presence of a chromosomal break that occurs in a gene that encodes a nuclear retinoic acid receptor.

CD2+, CD3-, CD56/NCAM+ malignant lymphoma with TCR beta gene rearrangement: a case report

A case of CD56/NCAM+ malignant lymphoma is reported. Only a rare malignant lymphoma cell showed azurophilic granules in the cytoplasm of Giesma-stained preparations, while electron microscopic examination revealed occasional cytoplasmic granules with paracrystalline inclusions. The most common phenotype seen in NK lymphomas, CD2+, CD3-, CD56+, CD16-, CD57-, was present in the case. Cases with this phenotype have been interpreted to represent either true NK lymphoma or T-cell lymphoma with NK expression. Genotyping, where performed, has shown TCR germline configuration. Our case showed TCR beta rearrangement indicating that the above phenotype can be associated with a peripheral T-cell lymphoma.

Aggressive pleomorphic CD2+, CD3-, CD56+ lymphoma with t(5;9)(q31;q34) abnormality

CD56-positive lymphoma is a recently described entity which is characterized by predominantly extranodal involvement and an aggressive clinical course. We report one such case with involvement of the bone marrow and spinal cord at presentation, and associated with reactive hemophagocytic syndrome. The lymphoma cells had a highly pleomorphic appearance which is uncommon in CD56-positive lymphoma. Cytogenetic studies revealed a t(5;9)(q31;q34) abnormality. Analysis of more cases is required to determine if this is a recurring chromosomal translocation characteristic of the group of aggressive CD56-positive lymphoma.

Longstanding proliferation of CD3 negative large granular lymphocytes preceding the development of high grade non-Hodgkin's lymphoma

A patient with a persistent CD3 negative large granular lymphocyte (LGL) proliferation with immunophenotypic and functional characteristics of natural killer cells is described. The LGL proliferation persisted and six years after diagnosis the patient developed a high grade B cell non-Hodgkin's lymphoma. Molecular studies demonstrated clonal B cell populations in the peripheral blood, distinct from that identified in the lymphoma, both at presentation with non-Hodgkin's lymphoma and at complete remission following combination chemotherapy. It is postulated that T cell dysregulation associated with the CD3 negative LGL proliferation may have led to B cell dysfunction and loss of normal B cell control, with the subsequent development of a clonal B cell lymphoproliferative disorder.

Acute agranular CD4-positive natural killer cell leukemia. Comprehensive clinicopathologic studies including virologic and in vitro culture with inducing agents

BACKGROUND

A 63-year-old male presented with fever, a subcutaneous nodule, gingival hypertrophy, lacrimal gland enlargement, and no lymphadenopathy or hepatosplenomegaly, but had anemia, thrombocytopenia, and peripheral blood (PB) plus bone marrow (BM) involvement by leukemic cells. There was minimal response to multiagent chemotherapy and local radiotherapy, with a survival of 6.5 months from disease diagnosis.

METHODS

The PB and/or BM leukemic cells were evaluated using electron microscopy (EM), immunohistochemistry, flow-cytometric immunophenotyping, cytochemistry, cytogenetics, Southern blot analysis for gene rearrangement and Epstein-Barr virus (EBV), polymerase chain reaction for EBV and human herpes virus-6 (HHV-6), and in vitro culturing with inducing agents.

RESULTS

The leukemic cells were agranular and monocytoid, with a hairy cell-like bone marrow biopsy infiltrate. Myeloperoxidase (MPO) and alpha-naphthyl butyrate esterase staining was negative, and periodic acid-Schiff staining was positive by light microscopy. Electron microscopy showed MPO negativity and a lack of parallel tubular arrays. The immunophenotype was CD3-, CD56+, CD4+, CD8-, CD15+, TCR1-, and TCR2-, with germline immunoglobulin and T-cell receptor genes and an abnormal karyotype (44XY, 5q-, -13, 13q+, -15). No genomic material for EBV or HHV-6 was detected. Cell cultures with butyrate and N,N-hexamethylene bis-acetamide suggested the possible induction of tumor cells to express a T-cell immunophenotype.

CONCLUSION

A case of clonal acute natural killer (NK) cell leukemia with an unusual morphology (agranular) and unique phenotype (CD3-, CD56+, CD4+, CD15+) is presented. Unlike as in other acute NK leukemias, EBV was negative; there was no evidence of HHV-6. The tumor cell, after culturing with differentiating agents, may have been induced to express a T-cell immunophenotype.

Epstein-Barr virus-associated natural killer-large granular lymphocyte leukemia

We describe the first case of an Epstein-Barr virus (EBV)-associated natural killer-large granular lymphocyte (NK-LGL) leukemia in the United States to the best of our knowledge. A 29-year-old woman of Japanese descent developed EBV infection after a blood transfusion as indicated by a rise in serum antibody titers. Peripheral blood and bone marrow aspirate smears demonstrated increased LGLs. Flow cytometry showed that these cells expressed NK-associated surface antigens. Cytogenetic analysis of the bone marrow aspirate showed two distinct but related clones with multiple copies of a modified 7 marker chromosome. Death followed colonic perforation. Findings at necropsy included bone marrow lymphocytosis and erythrophagocytosis, a mononucleosis-like lymphadenitis, atypical hepatitis with a mixed, predominantly T-cell infiltrate, interstitial pneumonitis, and multiorgan system vasculitis with perforation of the transverse colon. Epstein-Barr virus transcripts were identified in lymphocytes infiltrating liver and peripheral nerve by in situ hybridization. In addition, Southern blot analyses showed monoclonal bands superimposed on oligoclonal ladders of EBV termini in liver and lymph node. The identical episomal form of EBV was found in the bone marrow, lymph node, and liver. No immunoglobulin (Ig), T-cell receptor beta, or T-cell receptor gamma chain gene rearrangements were identified. These studies support the hypothesis that the LGL population was a neoplastic EBV-related clonal proliferation of NK cells.

CD56 (NCAM)-positive malignant lymphoma

CD56, a natural killer cell marker reactive with the neuronal-cell adhesion molecule (NCAM), identifies a group of lymphomas with distinctive clinicopathologic features. The disease affects mostly middle-aged adults who often present with fever, skin rash and hepatosplenomegaly in the absence of peripheral lymphadenopathy. Extranodal involvement is common, particularly the skin, aerodigestive tract and central nervous system. Histologically, an angiocentric and angiodestructive pattern of infiltrate is often seen, but the cytological spectrum of the lymphoma cells is very broad. Cytoplasmic granules, however, are frequently found when Giemsa-stained cytologic preparations are examined. Immunologically, CD56-positive lymphomas can be sub-classified into CD3-positive (T-cell) and CD3-negative (probably true natural killer cell) subtypes. T-cell receptor gene rearrangement can be demonstrated in the former cases, but not in the latter. Clinically, CD56-positive lymphomas are aggressive neoplasms.

Acute promyelocytic leukemia

Perhaps the most important advance in this field is not the specific actions of all-trans-retinoic acid in acute promyelocytic leukemia, but rather the conclusive documentation of differentiation as a practical and consistently effective method of treating human cancer. As a drug, all-trans-retinoic acid has certain undesirable pharmacologic properties that might be overcome by the use of alternative retinoids, such as 9-cis-retinoic acid, that are equally active against acute promyelocytic leukemia cells in vitro. In addition to retinoids that selectively activate RARs or RXRs, other ligands of the steroid-thyroid receptor superfamily, such as vitamin D3, glucocorticoids, and sex steroids also have cytodifferentiating actions in model systems. Numerous other agents can effect differentiation of neoplastic cells in such systems, including sodium butyrate, hexamethylene bisacetamide and its analogues, colony-stimulating factors, and interferons. Each of these compounds apparently acts through different pathways, and their activity may be greatly amplified when they are used in combination. Just as the practical usefulness of all-trans-retinoic acid in combination with conventional treatments continues to evolve, the use of differentiation agents in combination represents a novel and promising approach for oncologic therapy in the next decade. Although acute promyelocytic leukemia remains an "orphan" disease, its importance as a model for human neoplasia should not be minimized. The specific molecular lesion of acute promyelocytic leukemia is not shared by other cancers, but the physiologic actions of retinoids, their documented cytodifferentiating activity against a variety of human cancer cells in vitro, and their usefulness in cancer chemoprevention are clearly not mediated by identifiable mutations of retinoid receptors. The insights into transformation and leukemogenesis gained in acute promyelocytic leukemia may be a harbinger of further clinical applications and offer a glimpse into the next generation of cancer therapy.