Precursor B-lymphoblastic Lymphoma Research Articles

Non-Hodgkin lymphoma presenting with spinal cord compression: A population-based analysis of the NHL-BFM study group.

Spinal cord compression is a rare presentation of non-Hodgkin lymphoma (NHL) in children. We aimed to describe the prevalence, histological subtypes, clinical presentation, therapy, and outcome of those children in a population-based cohort. The chemotherapy regimen remained comparable over time. We retrospectively identified all children and adolescents with paresis as initial manifestations of the NHL between January 1990 and December 2020 from the NHL-BFM database. Characteristics, therapy, and outcome data were gathered from the database and patient files. Fifty-seven of 4779 children (1.2%) presented with initial paresis due to spinal cord compression. The median age was 10.3 years (range, 3.1-18.0 years), and 33% were female. Initial symptoms were paresis/weakness (n=50, 88%), back pain (n=33, 58%), paresthesia (n=23, 40%), and bladder dysfunction and/or constipation (n=22, 39%), persisting for a median of 14 days before diagnosis. Subtype distribution was mature B-NHL (n=41, 72%), precursor B-lymphoblastic lymphoma (LBL) (n=12, 21%), anaplastic large cell lymphoma (ALCL) (n=3, 5%), and T-LBL (n=1, 2%). Initial emergency therapy included surgery (70%) and/or chemotherapy/steroids (63%). Five-year event-free survival and overall survival (80%±5% and 82%±5%, respectively) were comparable with all other NHL patients. Neurological symptoms persisted in approximately one-third of surviving patients at the last follow-up. 1.2% of pediatric NHL patients presented with paresis from spinal cord compression mainly due to B-cell lymphomas. Neurological sequelae were observed in one-third of surviving patients.

Paediatric cutaneous lymphomas including rare subtypes: A 40-year experience at a tertiary referral centre.

Primary cutaneous lymphomas are neoplasms of the immune system with a distinct tropism for the skin and an absence of extracutaneous manifestations at the time of diagnosis. Studies focusing on cutaneous lymphomas in children and adolescents remain scarce and often do not encompass the rare subtypes. To address this knowledge gap by describing the clinical, histological and molecular characteristics of a large group of paediatric patients affected by primary cutaneous lymphoma. We also provided the Paediatric Primary Cutaneous Lymphoma Atlas that illustrates the clinicopathological spectrum of observed presentations, in the hope of supporting other physicians in the diagnostic process. Retrospective chart review of paediatric patients diagnosed with primary cutaneous lymphomas between 1980 and 2022 at the Paediatric Dermatology Unit of Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan. A total of 101 patients (58 males, 43 females) met the inclusion criteria. The most common subtypes were lymphomatoid papulosis (n = 48) and mycosis fungoides (n = 31). These were followed by primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorders (n = 7), primary cutaneous anaplastic large-cell lymphomas (n = 5), primary cutaneous marginal zone B-cell lymphomas (n = 3), primary cutaneous follicle centre lymphomas (n = 2), subcutaneous panniculitis-like T-cell lymphomas (n = 2), primary cutaneous peripheral T-cell lymphoma not otherwise specified (n = 1), primary cutaneous precursor B-lymphoblastic lymphoma (n = 1) and Sézary syndrome (n = 1). Clinical follow-up data covering a median of 70.8 months (range 1-324) were available for 74 patients, of whom three died due to cutaneous lymphoma. Our findings shed light on the peculiar aspects and long-term outcomes of paediatric cutaneous lymphomas, particularly emphasizing their distinctive features in comparison to their adult counterparts and exploring the less common subtypes. Further larger-scale studies are warranted to better characterize these entities and to achieve a more rapid and accurate diagnosis.

Primary Ovarian Non-Hodgkin Lymphoma- A Diagnostic Challenge with Clinicopathological Study of Eight Cases

Introduction: The involvement of the Female Genital Tract (FGT) by lymphoma is extremely rare, with ovaries being most commonly affected. Less than 1% of lymphomas present with ovarian involvement and less than 1.5% of ovarian neoplasms are of lymphoid origin. Secondary involvement of ovary by systemic lymphoma is more common than Primary Ovarian Lymphomas (POL) which is usually Primary Ovarian Non-Hodgkin lymphoma (PONHL) of B-cell lineage. Aim: To understand the clinicopathological and immuno- morphological features of Primary Ovarian Non-Hodgkin lymphoma. Materials and Methods: This was a descriptive retrospective study conducted at Department of Pathology, Kidwai Memorial Institute of Oncology, Bengaluru, Karnataka. India, for a duration of 14 years between July 2006 to June 2020. Eight cases of PONHL were identified from departmental archives and clinicopathological and Immunohistochemistry (IHC) findings of these tumours were analysed. Results: The PONHL constituted 0.4% of all Non-Hodgkin lymphoma (NHL) reported during the study period. The patients age ranged from 13-60 years with a mean age of 34 years. Among eight cases of PONHL, two cases were of Diffuse Large B-Cell Lymphoma (DLBCL), followed by one case each of High- Grade B-Cell Lymphoma, Not Otherwise Specified (HGBL, NOS), Follicular Lymphoma (FL), Burkitt Lymphoma (BL), Plasmablastic Lymphoma (PBL), Precursor B-Lymphoblastic Lymphoma (B-LBL), and precursor T-Lymphoblastic Lymphoma (T-LBL). Seven cases were staged IE (Ann Arbor staging system) while one case was designated as stage IIE. Conclusion: This was probably the first study on PONHL from India. The diagnosis of PONHL is challenging unless there is a high index of suspicion as these patients present with non specific pelvic symptoms and can be misdiagnosed as other epithelial, stromal or germ cell ovarian neoplasm which differs in treatment and prognosis. Histological examination with IHC and molecular testing are essential to establish a diagnosis.

Orbital precursor B‑lymphoblastic lymphoma involving the extraocular muscles in a 56‑year‑old male and a review of the literature

The aim of the present study was to describe a rare case of orbital precursor B-lymphoblastic lymphoma (B-LBL) in an adult. A 56-year-old male in complete remission of a gastric precursor B-LBL was referred to our orbital clinic due to rapid development of left-sided painless periorbital swelling, diplopia, and proptosis. Complete ophthalmoplegia was observed. Notably, magnetic resonance imaging showed swelling of the medial and inferior rectus muscles in the left orbit and biopsies were performed. Following histological diagnosis of precursor B-LBL, the patient was treated with radiotherapy (2Gy × 20) and chemotherapy according to the NOPHO ALL 2008 protocol. The disease progressed and the patient succumbed after 5 months. Histomorphologically, a lymphoblastic infiltrate was observed within the skeletal muscle tissue. The tumor cells were small and immature, and stained strongly for cluster of differentiating (CD)10, CD79a, paired box 5 and B cell lymphoma-2. The Ki-67 proliferative index was 90%. Multiplex ligation-dependent probe amplification and array comparative genomic hybridization detected whole chromosomal gain of X and 12, and both hemizygous and homozygous deletion on 9p comprising cyclin dependent kinase inhibitor 2A/B. Furthermore, array comparative genomic hybridization detected copy number imbalances consisting of focal or smaller deletions on chromosomes 1, 9, 10, 11 and 20. The final diagnosis was precursor B-LBL relapse in the extraocular muscles. Orbital precursor B-LBL is extremely rare in adults, and the diagnosis may be challenging to make. It is recommended to obtain material for cytogenetic and molecular analyses.

Primary cutaneous B-cell lymphoma: A single-center 5-year experience.

Skin is the second most common site for extranodal non-Hodgkin's lymphoma (NHL). Most primary cutaneous NHLs are of T-cell origin (70%). Primary cutaneous B-cell lymphoma (PCBCL) is a rare entity. Patients diagnosed with PCBCL between January 2012 and July 2017 at our center were retrospectively analyzed. Eight patients of PCBCL were diagnosed. Three patients (37.5%) were males while 5 patients (62.5%) were females. The median age at diagnosis was 45 years (range, 18-60 years). Scalp was the most common site of involvement (50% of the patients). Diffuse large B-cell lymphoma (DLBCL) was the most common histology (63%), with leg-type DLBCL diagnosed in 1 patient. Two patients had primary cutaneous follicle center lymphoma, whereas the remaining 1 patient had precursor B-lymphoblastic lymphoma. All 5 DLBCL cases were treated with CHOP chemotherapy, and rituximab was given to 3 patients. Of the primary cutaneous follicle center lymphomas, 1 patient with stage II disease was treated with CHOP and is alive without recurrence for the past 5 years, whereas the other patient is on observation alone. The patient with precursor B-lymphoblastic lymphoma was started on MCP-841 protocol; however, the patient did not complete the treatment and died after 11 months. PCBCL is a heterogeneous group of diseases and dividing them into subtypes, based on morphology and immunophenotype, has therapeutic implications.

B-Lymphoblastic Lymphomas Evolving from Follicular Lymphomas Co-Express Surrogate Light Chains and Mutated Gamma Heavy Chains

Follicular lymphoma (FL) is an indolent B-cell non-Hodgkin lymphoma able to transform into germinal center-type diffuse large B-cell lymphoma. We describe four extraordinary cases of FL, which progressed to TdT+CD20- precursor B-lymphoblastic lymphoma (B-LBL). Fluorescence in situ hybridization analysis showed that all four B-LBLs had acquired a MYC translocation on transformation. Comparative genomic hybridization analysis of one case demonstrated that in addition to 26 numerical aberrations that were shared between the FL and B-LBL, deletion of CDKN2A/B and 17q11, 14q32 amplification, and copy-neutral loss of heterozygosity of 9p were gained in the B-LBL cells. Whole-exome sequencing revealed mutations in FMN2, NEB, and SYNE1 and a nonsense mutation in KMT2D, all shared by the FL and B-LBL, and TNFRSF14, SMARCA2, CCND3 mutations uniquely present in the B-LBL. Remarkably, all four FL-B-LBL pairs expressed IgG. In two B-LBLs, evidence was obtained for ongoing rearrangement of IG light chain variable genes and expression of the surrogate light chain. IGHV mutation analysis showed that all FL-B-LBL pairs harbored identical or near-identical somatic mutations. From the somatic gene alterations found in the IG and non-IG genes, we conclude that the FLs and B-LBLs did not develop in parallel from early t(14;18)-positive IG-unmutated precursors, but that the B-LBLs developed from preexistent FL subclones that accumulated additional genetic damage.

Complex MLLrearrangement in non-infiltrated bone marrow in an infant with stage II precursor B-lymphoblastic lymphoma

Precursor B-lymphoblastic lymphoma cells are indistinguishable by morphology, and immune phenotype from lymphoblasts in acute leukemia which in infancy is associated with MLL rearrangements and a poor prognosis. The role of MLL gene deregulation in rare cases of isolated lymphoblastic lymphoma in infants is obscure. We report the case of a 10-month-old child who presented with a cutaneous nodule on the left foot. Histological diagnosis was precursor B-lymphoblastic lymphoma. The young age of the patient motivated us to investigate the presence of an MLL rearrangement. Cytogenetic analysis was performed by fluorescence in situ hybridization (FISH), and the genomic fusion partner of MLL was identified by long-distance inverse (LDI-)PCR and confirmed by direct PCR. Fluorescence in situ hybridization screening of paraffin-embedded formalin-fixed tissue indeed revealed the presence of an MLL rearrangement. The genomic fusion partner was identified as AF10 by DNA sequencing of the MLL breakpoint region. The MLL-AF10 fusion gene was further detected in cytologically normal pretreated bone marrow. Treatment was started with standard four-drug induction chemotherapy. Because of the unfavorable outcome associated with MLL rearrangements in infant leukemia, we intensified postremission treatment according to the Interfant-06 study protocol. The child is in continuous first remission 36 months after diagnosis. This is the first report of submicroscopic bone marrow involvement in MLL-rearranged isolated cutaneous B-cell precursor lymphoma in an infant. To prospectively address the role of MLL rearrangements in extramedullary B-lymphoblastic malignancies in infants, we suggest to assess both tumors and non-infiltrated bone marrow for the presence of this genetic abnormality.

Unusual presentation of Precursor B Lymphoblastic Lymphoma originating from the stomach: One more case and review of the literature

Precursor B lymphoblastic lymphoma (PBL) is an aggressive neoplasm of precursor lymphocytes of B-cell lineage. Extranodal sites are often affected, however gastrointestinal involvement is rarely encountered. We report a case of PBL diagnosed in gastric biopsy of a 72-year-old female. Endoscopy showed multiple polypoid lesions in the stomach. Histologically, the tumor cells exhibited blastic morphology and immunohistochemical expression of terminal deoxynucleotidyl transferase (TdT), CD79a, CD20, CD10 and PAX-5, whereas they were CD34, MPO, and CD3 negative. The diagnosis of this rare entity in unusual extranodal sites such as the stomach is challenging, and it is based on detailed histopathological and immunohistochemical analysis combined to clinical correlations.

Precursor B-lymphoblastic Lymphoma Involving an Intracardiac Mass and Myocardial Infiltration: A Case Report

We report the case of a 17-year-old man with precursor B-lymphoblastic lymphoma involving an intracardiac mass and myocardial infiltration. Intensified chemotherapy followed by autologous peripheral blood stem cell transplantation resulted in long-term complete remission for over 5 years. As the most frequent sites of B-lymphoblastic lymphoma involvement are the skin, soft tissue, bone, and lymph nodes, reports of cases harboring cardiac involvement are relatively few. This is a rare case of B-lymphoblastic lymphoma displaying cardiac involvement, in which cardiac infiltration was one of the initial manifestations.

Expression of the Brain Transcription Factor OTX1 Occurs in a Subset of Normal Germinal-Center B Cells and in Aggressive Non-Hodgkin Lymphoma

The roles in brain development. Previous studies have shown the association between OTX2 and OTX1 with anaplastic and desmoplastic medulloblastomas, respectively. Here, we investigated OTX1 and OTX2 expression in Non-Hodgkin Lymphoma (NHL) and multiple myeloma. A combination of semiquantitative RT-PCR, Western blot, and immunohistochemical analyses was used to measure OTX1 and OTX2 levels in normal lymphoid tissues and in 184 tumor specimens representative of various forms of NHL and multiple myeloma. OTX1 expression was activated in 94% of diffuse large B-cell lymphomas, in all Burkitt lymphomas, and in 90% of high-grade follicular lymphomas. OTX1 was undetectable in precursor-B lymphoblastic lymphoma, chronic lymphocytic leukemia, and in most marginal zone and mantle cell lymphomas and multiple myeloma. OTX2 was undetectable in all analyzed malignancies. Analysis of OTX1 expression in normal lymphoid tissues identified a subset of resting germinal center (GC) B cells lacking PAX5 and BCL6 and expressing cytoplasmic IgG and syndecan. About 50% of OTX1(+) GC B cells co-expressed CD10 and CD20. This study identifies OTX1 as a molecular marker for high-grade GC-derived NHL and suggests an involvement of this transcription factor in B-cell lymphomagenesis. Furthermore, OTX1 expression in a subset of normal GC B cells carrying plasma cell markers suggests its possible contribution to terminal B-cell differentiation.

Intraocular Lymphoma: Diagnostic Approach and Immunophenotypic Findings in Vitrectomy Specimens

Diagnosis and classification of primary intraocular lymphoma can be challenging because of the sparse cellularity of the vitreous specimens. To classify and clinically correlate intraocular lymphoma according to the World Health Organization (WHO) classification by using vitrectomy specimens. Clinical history, cytologic preparations, flow cytometry reports, and outcome of 16 patients diagnosed with intraocular lymphoma were reviewed. The study group included 10 women and 6 men. The mean age of the patients was 63 years (range, 19-79 years). Eleven patients had central nervous system involvement and 6 patients had systemic involvement. All cases were adequately diagnosed and classified according to the WHO classification by using combination of cytologic preparations and 4-color flow cytometry with a limited panel of antibodies to CD19, CD20, CD5, CD10, and kappa and lambda light chains. The cases included 9 primary diffuse large B-cell lymphomas of the CNS type; 2 diffuse large B-cell lymphomas, not otherwise specified; 1 extranodal, low-grade, marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT); 1 precursor B-lymphoblastic lymphoma; and 3 peripheral T-cell lymphomas, not otherwise specified. Of note, all 11 cases of diffuse large B-cell lymphoma were CD10-. All the patients received systemic chemotherapy and radiation therapy. Only 4 patients were free of disease at last follow-up (range, 18 months to 8 years), with severe visual loss. Intraocular lymphoma cases can be adequately classified according to the WHO classification. Diffuse large B-cell lymphoma, CD10- and most likely of non-germinal center B-cell-like subgroup, is the most common subtype of non-Hodgkin lymphoma in this site, in contrast to ocular adnexal lymphoma for which MALT lymphoma is the most common subtype.

Precursor B-Lymphoblastic Lymphoma Presenting as a Solitary Bone Tumor Mimicking Osteomyelitis on MRI

Precursor B-Lymphoblastic Lymphoma Presenting as a Solitary Bone Tumor Mimicking Osteomyelitis on MRI

The impact of age and gender on biology, clinical features and treatment outcome of non‐Hodgkin lymphoma in childhood and adolescence

We analysed the impact of age and gender on biology and outcome of 2084 patients diagnosed with non-Hodgkin lymphoma (NHL) between October 1986 and December 2002 and treated according to the Berlin-Frankfurt-Münster (BFM) multicentre protocols NHL-BFM-86, -90 and -95. Median age at diagnosis was 8.0 years for 97 precursor B-lymphoblastic lymphoma (pB-LBL) patients, 8.8 years for 335 T-lymphoblastic lymphoma (T-LBL) patients, 8.4 years for 1004 Burkitt's lymphoma/leukaemia (BL/B-AL) patients, 11.4 years for 173 diffuse large B-cell lymphoma (centroblastic subtype) (DLBCL-CB) patients, 13.2 years for 40 primary mediastinal large B-cell lymphoma (PMLBL) patients and 10.8 years for 215 anaplastic large-cell lymphoma (ALCL) patients (P < 0.00001). The male:female ratio was 0.9:1 for pB-LBL and PMLBL, 1.7:1 for DLBCL-CB, 1.8:1 for ALCL, 2.5:1 for T-LBL and 4.5:1 for BL/B-AL (P < 0.00001). The probability of event-free survival at 5 years (5-year pEFS) was 85 +/- 1% for all 2084 patients [median follow-up 5.7 (0.1-15.9) years], and was significantly superior for male T-LBL and DLBCL-CB patients. Comparing age-groups 0-4, 5-9, 10-14 and 15-18 years, pEFS was inferior for the youngest patients only in the pB-LBL- and ALCL-groups. T-LBL and DLBCL-CB adolescent females had worse outcome than younger girls while age had no impact on pEFS for boys. We conclude that the distribution of age and gender differed between NHL-subtypes. The impact of gender on outcome differed between NHL subgroups. The prognostic impact of age differed not only by NHL-subtype but also according to gender in some subtypes.

Coexpression of CD43 by Benign B Cells in the Terminal Ileum

Expression of CD43 by B cells is often used as a diagnostic criterion in favor of a B-cell lymphoproliferative disorder, including small lymphocytic lymphoma/chronic lymphocytic leukemia, mantle cell lymphoma, Burkitt lymphoma, precursor B-lymphoblastic lymphoma, and a subset of marginal zone B-cell lymphomas. Benign B cells generally do not coexpress CD43. The authors analyzed 20 biopsies of the terminal ileum for nonneoplastic disease for expression of CD43 and compared them with other sites and with CD20, CD138, and CD3 reactivity. The majority of cases (85%) showed strong coexpression of CD43 by benign perifollicular B cells. The presence of CD43 coexpression in B-cell populations of the terminal ileum, including those of Peyer's patches, should not be used as a diagnostic parameter to differentiate extranodal marginal zone B-cell lymphoma of MALT type from reactive processes.

Immunohistochemical detection of ZAP-70 in 341 cases of non-Hodgkin and Hodgkin lymphoma

Using immunohistochemical methods, we evaluated zeta-associated protein (ZAP)-70 expression in 341 cases of non-Hodgkin and Hodgkin lymphoma. In B-cell NHL, ZAP-70 was positive in five of six (83%) precursor B-lymphoblastic lymphoma, 11 of 37 (30%) chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), five of 39 (13%) mantle cell lymphoma, one of 12 (8%) Burkitt lymphoma, and one of 12 (8%) nodal marginal zone B-cell lymphoma. In 22 cases of CLL/SLL, seven of nine (78%) with unmutated IgVH genes expressed ZAP-70, compared with one of 13 (8%) with mutated IgVH genes (P=0.0015 Fisher's exact test). ZAP-70 expression was not detected in diffuse large B-cell lymphoma (n=26), extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (n=24), follicular lymphoma (n=21), plasma cell myeloma/plasmacytoma (n=10), lymphoplasmacytic lymphoma (n=10), or splenic marginal zone lymphoma (n=6). In T/NK-cell NHL, ZAP-70 was positive in all extranodal natural killer (NK) / T-cell lymphoma, nasal-type (n=6) and enteropathy-type T-cell lymphoma (n=4), four of five (80%) subcutaneous panniculitis-like T-cell lymphoma, six of eight (75%) mycosis fungoides, three of five (60%) precursor T-lymphoblastic lymphoma, 10 of 17 (59%) peripheral T-cell lymphoma, two of four (50%) blastic NK-cell lymphoma, one of three (33%) T-cell prolymphocytic leukemia, 13 of 52 (25%) anaplastic large cell lymphoma, and one of six (17%) angioimmunoblastic T-cell lymphoma. Seven of 12 (58%) cutaneous CD30-positive lymphoproliferative disorders were also ZAP-70-positive. In Hodgkin lymphoma, ZAP-70 was negative in neoplastic cells in all cases tested. ZAP-70 staining in B-cell lymphomas and reactive T cells was predominantly nuclear with variable cytoplasmic staining. By contrast, ZAP-70 staining in T/NK-cell lymphomas was heterogeneous, and a shift from predominantly nuclear to predominantly cytoplasmic staining was observed, particularly in those neoplasms with high-grade morphology. In summary, ZAP-70 is expressed by many lymphoma types, correlates with immunoglobulin heavy-chain variable region gene mutational status in CLL/SLL, and can be detected reliably using immunohistochemical methods.

Primary cardiac precursor B lymphoblastic lymphoma in a child: A case report and review of the literature

We describe an extremely rare case of primary cardiac precursor B lymphoblastic lymphoma (B-LBL) in a 10-year-old boy who presented with nonspecific complaints of fatigue and vomiting for 2 weeks and an episode of syncope. Chest X-ray showed cardiomegaly and echocardiography revealed a large right atrial mass, which was successfully resected. Pathology showed precursor B-LBL arising in the heart and there was no evidence of disease at any extracardiac site. A brief review of the literature is also presented.

Absence of somatic hypermutation of immunoglobulin heavy chain variable region genes in precursor B-lymphoblastic lymphoma: a study of four cases in childhood and adolescence.

Somatic mutation (SM) analysis provides a useful tool for understanding the suitable stage of differentiation of normal and neoplastic B cells. B-cell precursor neoplasms are considered to be somatically premutational. However, no reports have been made on the sequence analysis of SM in rearranged immunoglobulin heavy chain variable region (VH) genes in precursor B-lymphoblastic lymphoma (PB-LBL); as for B-cell acute lymphoblastic leukemia (B-ALL), the variable frequency of SM of the VH genes has been described. To better distinguish PB-LBL from B-ALL based on the stage at which differentiation occurs, we analyzed the SM of the VH genes in 4 children and adolescents with PB-LBL. In all 4 cases, there was no SM in complementarity-determining regions 1, 2, and 3 and in framework regions 2 and 3 of the VH genes, except for 1 mutation in 1 of 2 polymerase chain reaction products from 1 patient. Our data showed the absence of SM of lymphoma cells in PB-LBL, in addition to the developmentally regulated rearrangement of VH genes at the stage of B-cell precursor cells. The lack of mutation in VH gene sequences suggests that SM may differ between PB-LBL and B-ALL.

Differentiating Lymphoblastic Lymphoma and Ewing's Sarcoma: Lymphocyte Markers and Gene Rearrangement

We encountered a child with an intraosseous small round cell tumor that was negative for LCA, CD20 (L26), and CD3 and positive for vimentin, CD99 (MIC-2), and periodic acid-Schiff. The tumor exhibited rosette-like formations. This case was initially interpreted as Ewing's sarcoma (ES); however, additional studies revealed positivity for CD79a, CD43, and TdT expression, and an immunoglobulin heavy chain gene rearrangement (IgH-R) by polymerase chain reaction (PCR) established this to be a precursor B-lymphoblastic lymphoma. Because the differential diagnosis of ES and lymphoblastic lymphoma can be difficult and the differential diagnostic value of leukocyte antigens and immunoglobulin heavy chain gene rearrangement studies have not been fully evaluated, we conducted a more extensive investigation on 33 (21 soft tissue and 12 intraosseous) ES cases. Cases were retrieved from the files of the Department of Pathology at Georgetown University and from the Soft Tissue Registry of the Armed Forces Institute of Pathology. The cases were studied by light microscopy, immunohistochemistry, and PCR for IgH-R and T cell receptor gamma chain gene rearrangement (Tγ-R). There were 17 females and 16 males; the mean age was 29.3 years. Locations included the extremities (n = 17) and trunk (n = 16). All cases fit the ES spectrum by light microscopy and immunohistochemistry, as previously determined, and were negative for lymphoid markers (LCA, CD3, CD20, CD43, CD79a, and TdT), CD10 and CD34. CD99 was positive in 31/33 and bcl-2 was weakly positive in 13/33 cases. All 21 cases studied for gene rearrangements by PCR were negative for IgH-R and Tγ-R. Distinction of intraosseous lymphoblastic lymphoma from ES may be difficult because lymphomas may occasionally exhibit unexpected morphologic and immunophenotypic properties including LCA, CD3 and CD20 negativity and cytokeratin positivity. Additional analysis using CD79a, CD43, TdT, and PCR should be performed to avoid misdiagnosis. True ES is negative for lymphoid markers including CD79a, CD43, and TdT, as well as for IgH-R and Tγ-R.